Migrate data from an Alibaba Cloud simple application server to an ECS instance

If your Simple Application Server (SAS) cannot meet your business configuration requirements, you can smoothly migrate data from the simple application server to an Elastic Compute Service (ECS) instance to implement more flexible resource configuration. The source simple application server and the destination ECS instance must belong to the same Alibaba Cloud account but can reside in the same region or different regions. This topic describes how to use Server Migration Center (SMC) to migrate data from a simple application server to an ECS instance.

Note

We recommend that you preferentially use the image copy and image sharing features of Simple Application Server to migrate data from a simple application server to an ECS instance. For more information, see Migrate data from a simple application server to an ECS instance. If the preceding features cannot meet your requirements, you can use the method described in this topic to migrate data from a simple application server to an ECS instance.

Scenarios

(Recommend) Migrate data from a simple application server to an ECS custom image in the same region or across regions.
If you have not purchased a destination ECS instance, you can migrate data from a simple application server to an ECS custom image and then create an ECS instance based on the custom image.
Migrate data from a simple application server to an existing ECS instance in the same region.
If you have purchased a destination ECS instance, and the storage and operating system of the simple application server are the same as the storage and operating system of the destination ECS instance, you can migrate data from the simple application server to the existing ECS instance.
Warning
After you migrate the data, the original data in the destination ECS instance is deleted, and the data on the simple application server is not affected. If the destination ECS instance contains important data, we recommend that you do not migrate data from a simple application server to the destination ECS instance.

Impacts

Before the migration, take note of the information in the following table.

Item	Description

Item	Description
Data directory	During migration, SMC can automatically generate a disk partition structure that is as consistent as possible with that of the source server based on the disk partition structure of the source server. You can adjust the partition structure of the destination disk as needed, including the partition size and location sequence, transfer mode, and whether to enable LVM. By default, all the disks of the server are migrated, but the following conditions still need to be considered: If no mount targets exist under the data disk, the data disk is not migrated. If you do not need to migrate some partition directories, you can choose not to migrate these disks after adjusting the disk partition structure. For more information, see Step 2: Migration configurations.
Intermediate instance	Do not perform operations on the intermediate instance during the migration. To prevent migration failures, do not stop, start, restart, or release the intermediate instance or change the billing method of the intermediate instance during the migration process. After the migration is complete, SMC automatically releases the intermediate instance. Note To run a migration job, SMC creates a pay-as-you-go temporary intermediate instance named `No_Delete_SMC_Transition_Instance` within your Alibaba Cloud account. For more information, see the "What specifications are available for intermediate instances?" section of the FAQ about Server Migration Center (SMC) topic. When you migrate a server to an ECS instance, the ECS instance serves as the intermediate instance. The instance is not automatically released. Formore information, see How it works.
IP address	After the migration, the IP address of your server is changed, which may cause service interruption. We recommend that you perform the migration during off-peak hours. If the business involves the configuration of IP addresses, modify the domain name resolution and ICP filing after migration. If a domain name has been bound to the source server, the public IP address of the server is changed after the migration. In this case, you must resolve the domain name to the new public IP address of the server. For more information, see Add an A record for a website domain name. If you want to keep the private IP address unchanged, perform the following operations: Migrate the source server to the ECS Image: After the migration, modify the private IP address when creating an ECS instance through the cloud server image. For more information, see Specify the primary private IPv4 address when creating an ECS instance. Migrate the source server to the Instance: You can modify the IPv4 private IP address of the instance in the advanced configuration of Migration settings, or after the migration. For more information, see Change the primary private IPv4 address for an existing ECS instance.
Underlying hardware	After the migration, the underlying hardware may change, and the application licenses that are associated with the underlying hardware may become invalid. Perform checks based on your business requirements.

Prerequisites

The preparations for server migration are complete. For more information, see Before you begin.
If you want to migrate data from a simple application server to an existing ECS instance, the following requirements must be met:
- Back up the important data on the destination ECS instance to an image, snapshot, or storage device other than the instance.
- The operating system of the destination ECS instance is the same as that of the source server.
- The number of data disks attached to the destination ECS instance is greater than or equal to that of data disks attached to the source server. Otherwise, the disk data of the source server cannot be migrated to the destination ECS instance. In this case, you must attach more data disks to the ECS instance. For more information, see Attach a data disk.
- The capacity of the system disk and data disks attached to the ECS instance is larger than or equal to that of the system disk and data disks attached to the source server. If you want to shrink the system disk and data disks attached to the source server, make sure that the capacity of the system disk and data disks attached to the destination ECS instance is larger than or equal to the size of the data on the system disk and data disks attached to the source server. Otherwise, data of the source server cannot be fully migrated to the destination ECS instance. In this case, you must scale up the data disks and system disk. For more information about how to resize a cloud disk, see Overview.

Procedure

Step 1: Import the information about a migration source

Migration sources can be servers of a variety of types to migrate, such as servers in data centers, VMs, and hosts on third-party cloud platforms. SMC supports multiple methods to import the information about migration sources. You can select a method based on your business requirements. For more information, see the How do I select the method to import the information about a migration source? section of the "FAQ" topic.

(Recommend) Use the CLI

Use the SMC console

Use the SMC client

Important

The source server must be accessible over the Internet.

Log on to the Server Migration Center (SMC) console.
In the left-side navigation pane, choose Migrate to Cloud > Server Migration.
On the Server Migration page, click Import Migration source.

Configure the parameters as prompted and copy the activation code command. The following table describes the parameters.

Parameter	Description
Workgroup	Optional. Suitable for scenarios involving batch migration to ECS image. For single server migration, please skip this parameter. You can manage multiple migration sources in the same workgroup. Automatic incremental synchronization must be enabled for migration sources associated with the workgroup during migration. For more information, see Batch migration of servers. If a workgroup has not been created, click Create a New Workgroup.
Migration Source Type	The type of the migration source. Select Physical Server or VM.
Import Method	Select Use CLI to Import Server. Generate an activation code and a command, and run the command on the migration source.
Migration Source Quota	The number of migration sources whose information you want to import by using the activation code. Valid values: 1 to 1000. Default value: 200.
Validity Period	The validity period of the activation code. Unit: day. Valid values: 1 to 90. Default value: 90.
Activation Code	The activation code. Perform the following steps to generate the activation code and copy the generated command: Click Generate. Click the Linux Shell or Windows Powershell tab based on the operating system of the source. Click Copy to copy the activation code command.

Log on to the source server and paste and run the copied command as an administrator to import the information about the migration source.
Linux server
Windows server
1. Log on to the Linux server.
2. Paste and run the copied command as an administrator to import the information about the migration source.
  After the command is run, if a message similar to Import Source Server [s-bp18x8751kgz2oyh****] Successfully! is returned, the information about the migration source is imported.
1. Log on to the Windows server.
2. Open Windows PowerShell as an administrator.
3. Run the copied command to import the information about the migration source.
  After the command is run, if a message similar to Import Source Server [s-bp19rlidl3mwuptc****] Successfully! is returned, the information about the migration source is imported.
On the Server Migration page in the SMC console, view the status of the migration source in the Real-time Migration Status column.
- If the status of the migration source is Migration SourceOnline, the information about the migration source is imported.
- If the migration source is in another state, the information fails to be imported. In this case, troubleshoot the failure based on the following solutions and import the information about the migration source again:
  - Troubleshoot the failure based on the message displayed in the SMC console or the log file in the directory where the SMC client is installed. By default, the SMC client is installed in the following directory:
    - Windows server: C:\smc
    - Linux server: /smc
  - For more information about frequently asked questions (FAQ) and solutions, see FAQ about Server Migration Center (SMC) and Errors occurred during a server migration.

Important

The source server must be accessible over the Internet.

If you want to import the information about a migration source as a Resource Access Management (RAM) user, make sure that the following permissions are granted to the RAM user:
- AliyunRAMReadOnlyAccess. For more information, see Grant permissions to a RAM user.
- AliyunCloudShellFullAccess. For more information, see Authorize RAM users.

Log on to the Server Migration Center (SMC) console.
In the left-side navigation pane, choose Migrate to Cloud > Server Migration.
On the Server Migration page, click Import Migration source.

On the Import Migration source page, configure the parameters based on the type of your migration source.

Parameter	Description
Workgroup	Optional. Suitable for scenarios involving batch migration to ECS image. For single server migration, please skip this parameter. You can manage multiple migration sources in the same workgroup. Automatic incremental synchronization must be enabled for migration sources associated with the workgroup during migration. For more information, see Batch migration of servers. If a workgroup has not been created, click Create a New Workgroup.
Migration Source Type	The type of the migration source. Select Physical Server or VM.
Import Method	Select Import through Console. In the SMC console, manually enter the public IP address, port number, and SSH user password of the source server, and authorize SMC to remotely connect to the source server to automatically import the migration source.
Migration Source Name	The name of the migration source. The name must be 2 to 128 characters in length. The name must start with a letter but cannot start with `http://` or `https://`. The name can contain letters, digits, colons (:), underscores (_), and hyphens (-).
OS Type	The type of the operating system of the source server. Select Linux or Windows based on your business requirements. Important If you select Windows as the operating system, you must install OpenSSH. For more information, see the How do I install OpenSSH on a Windows server? section of the "FAQ" topic.
IP Address	The IPv4 address that is used to access the migration source over the Internet. Example: 120.55.XX.XX.
Port	The SSH port number of the migration source. Valid values: 1 to 65535. Default value: 22.
Username	The username with administrator permissions, used to log on to the operating system of the migration source. Linux: The default username is `root`. Windows: The default username is `Administrator`.
Password	The password corresponding to the username.

After you configure the parameters, click Import.
SMC automatically launches CloudShell to perform the import. The import process takes about 3 to 10 minutes. Wait until the import is complete.
On the Server Migration page in the SMC console, view the status of the migration source in the Real-time Migration Status column.
- If the status of the migration source is Migration SourceOnline, the information about the migration source is imported.
- If the migration source is in another state, the information fails to be imported. In this case, troubleshoot the failure based on the following solutions and import the information about the migration source again:
  - Troubleshoot the failure based on the message displayed in the SMC console or the log file in the directory where the SMC client is installed. By default, the SMC client is installed in the following directory:
    - Windows server: C:\smc
    - Linux server: /smc
  - For more information about frequently asked questions (FAQ) and solutions, see FAQ about Server Migration Center (SMC) and Errors occurred during a server migration.

For more information about the SMC client, see Use the SMC client.

Log on to the Server Migration Center (SMC) console.
In the left-side navigation pane, choose Migrate to Cloud > Server Migration.
On the Server Migration page, click Import Migration source.

On the Import Migration source page, configure the parameters. The following table describes the parameters.

Parameter	Description
Migration Source Type	The type of the migration source. Select Physical Server or VM.
Import Method	Select Use Client to Import Server. Manually download and install the SMC client on the source server.
Description	The description about how to download the SMC client. Read the information in the Description section and follow the prompts to download, install, and activate the corresponding SMC client based on the CPU architecture (ARM or x86) and bit version (32-bit or 64-bit) of the operating system of the migration source.

Import the information about the migration source.
Perform the operations based on the operating system of the migration source.
Important
During the migration, do not shut down the SMC client until the migration is complete. Otherwise, the migration source is disconnected from the SMC console, and the migration fails.
Windows server
Linux server
1. You can use a remote connection tool that supports file transfer. For example, you can use WinSCP to upload the SMC client package to the source Windows server.
2. On the source Windows server, use the built-in decompression tool of Windows or the decompression tool that you install to decompress the SMC client package.
3. In the SMC client folder that corresponds to the source server, run the SMC client.
  To run the Windows GUI version, double-click the go2aliyun_gui.exe file.
  To run the Windows CLI version, double-click the go2aliyun_client.exe file.
  Note
  When you run the program, you must click OK to confirm that you have the administrator permissions.
4. Obtain an activation code or AccessKey pair.
  (Recommend) Obtain an activation code: In the Description section in the SMC console, click Generate and copy the generated activation code information.
  Obtain an AccessKey pair: An AccessKey pair consists of an AccessKey ID and an AccessKey secret. If no AccessKey pair is created, create one first. For more information, see Obtain an AccessKey pair.
5. Enter the activation code or AccessKey pair as prompted.
  To run the Windows GUI version, enter the activation code or AccessKey pair in the Token Id/AK and Token Code/SK fields and click Start. For more information, see Use the SMC client.
  To run the Windows CLI version, enter the obtained access_access_token_id and access_token_code and press the Enter key.
  If the information about the migration source is imported, a message similar to the following one is returned: Import Source Server [s-bp18x8751kgz2oyh****] Successfully!
1. You can use a remote connection tool that supports file transfer. For example, you can use WinSCP to upload the SMC client package to the source Linux server.
2. Connect to the source Linux server and decompress the SMC client package.
  Linux 64-bit Generic is used in the example. Run the following command to decompress the package. If you use another version of the SMC client, replace the package name in the command with the name of your SMC client.
  
  tar xf go2aliyun_client_linux_x86_64.tar.gz
  
  Note
  Linux ARM64 supports the g6r general-purpose instance family and the c6r compute-optimized instance family. For more information about instance types, see the "Arm-based enterprise-level computing instance families" section of the Overview of instance families topic.
3. (Optional) Exclude the files or directories that you do not need from the migration. For more information, see the How do I exclude files or directories from a migration job? section of the "FAQ" topic.
  Important
  If you enable the block replication feature, you cannot exclude files or directories from the migration job.
4. Obtain an activation code or AccessKey pair.
  (Recommend) Obtain an activation code: In the Description section in the SMC console, click Generate and copy the generated activation code information.
  Obtain an AccessKey pair: An AccessKey pair consists of an AccessKey ID and an AccessKey secret. If no AccessKey pair is created, create one first. For more information, see Obtain an AccessKey pair.
5. In the SMC client folder, run the following commands to run the SMC client.
  
  cd go2aliyun_client_linux_x86_64 sudo chmod +x go2aliyun_client sudo ./go2aliyun_client
6. Enter the activation code or AccessKey pair as prompted. The following figure shows an example of an activation code.
  The following messages may appear after you enter the activation code.
  If no snapshot dependency is installed on your source server, a message appears. The following figure shows the details of the message. You can decide whether to install a snapshot dependency based on whether you enable the block replication feature.
  If you want to enable block replication for the migration, enter yes to automatically install a snapshot dependency.
  If you do not want to enable block replication for the migration, enter no.
  Important
  If the snapshot dependency fails to be installed, do not enable block replication when you create a migration job. Otherwise, the migration may fail.
  The rsync tool is installed on most mainstream migration sources. If rsync is not installed on the migration source, the SMC client displays a message. Enter yes to install rsync, as shown in the following figure.
  If SELinux is enabled on the migration source, a message that prompts you to disable SELinux appears. Enter yes to disable SELinux. The following figure shows how to disable SELinux.
  If the information about the migration source is imported, a message similar to the following one is returned: Import Source Server [s-bp11npxndknsycqj****] Successfully!.
  Note
  If the information about the migration source fails to be imported, you can troubleshoot the issue based on the returned message. After you fix the issue, run the following commands to exit the background program and re-import the information about the migration source. For more information about FAQ and solutions, see FAQ about Server Migration Center (SMC) and Errors occurred during a server migration.
  
  sudo ./go2aliyun_client --abort sudo ./go2aliyun_client
On the Server Migration page in the SMC console, view the status of the migration source in the Real-time Migration Status column.
- If the status of the migration source is Migration SourceOnline, the information about the migration source is imported.
- If the migration source is in another state, the information fails to be imported. In this case, troubleshoot the failure based on the following solutions and import the information about the migration source again:
  - Troubleshoot the failure based on the message displayed in the SMC console or the log file in the directory where the SMC client is installed. By default, the SMC client is installed in the following directory:
    - Windows server: C:\smc
    - Linux server: /smc
  - For more information about frequently asked questions (FAQ) and solutions, see FAQ about Server Migration Center (SMC) and Errors occurred during a server migration.

Step 2: Migration configurations

Find the migration source that you want to manage and click Start Migration in the Actions column.

Configure the parameters and click Start Migration.

Configure the basic parameters described in the following table.

Parameter	Description	Example
Migration Job Name	The name of the migration job.	Server migration
Job Description	The description of the migration job.	test
Destination Type	Required. The type of the destination. Select a destination type based on the actual migration scenario. ECS Image ECS Instance Container Image Migrate the source server to an ECS custom image and then use the custom image to create an ECS instance. If you set the Destination Type parameter to ECS Image, the following parameters are displayed: Destination Region: the Alibaba Cloud region to which you want to migrate the source server. This parameter is required. For more information about regions, see Regions and zones. Image Name: the name of the destination custom image generated by SMC for the source server. Migrate the source server to an existing ECS instance whose configurations such as storage and operating system match those of the source server. Important During the migration, the operating system of the destination ECS instance is replaced, and automatic snapshots of the system disk are released and cannot be recovered. If you want to retain automatic snapshots for future needs or for data security considerations, you can manually cancel the release of automatic snapshots together with the disk before the migration. For more information, see Delete automatic snapshots while releasing a disk. If you set the Destination Type parameter to ECS Instance, the following parameters are displayed: Destination Region: the Alibaba Cloud region to which you want to migrate the source server. This parameter is required. For more information about regions, see Regions and zones. Destination Instance: the ECS instance that is used as the destination instance. Migrate the source server to ACR. You can migrate only Linux servers of the x86 architecture as container images. For more information, see Migrate a server to Container Registry.	ECS Image
Migration Test	Specifies whether to enable the migration test feature. This feature helps you understand the feasibility and risks of a migration job before the migration job starts and provides solutions to identified issues. You can also obtain information such as the amount of data to be migrated, migration speed, and total duration of the migration. This helps reduce the issues and losses that may occur during the actual migration. During the test, you are charged for pay-as-you-go resources. By default, Migration Test is turned on. Warning If you set the Destination Type parameter to ECS Instance, snapshots are created for all disks of the destination ECS instance. If the migration test is abnormal or the Execution Method parameter is set to Test Only, the disk snapshots are automatically rolled back. During the migration test, the destination ECS instance is unavailable and all data is lost. Make sure that the destination ECS instance does not have important data. For more information, see Configure a migration test.	Keep the default setting
Execution Method	The mode in which the migration job is run. Select an execution method based on whether Migration Test is turned on. When Migration Test is turned on When Migration Test is turned off Test Only: The system performs only the migration test. After the migration test is complete, you must manually start the server migration job. Test and Migrate: The system performs the migration test. After the migration test is complete, if no test items are in the Critical state, the system automatically starts the server migration job. This is the default value. Migrate Now: The migration job starts immediately after it is created. This is the default value. Migrate Later: The migration job automatically starts at the specified time after it is created. Note The earliest time that you can specify to run a migration job is 10 minutes after the job is created. Create Only: After the migration job is created, you must click Start Migration Job in the Actions column to manually start the migration job.	Keep the default setting
Automatic Incremental Synchronization	Specifies whether SMC automatically synchronizes incremental data of the migration source to Alibaba Cloud. By default, this feature is disabled. If you enable this feature, you must configure the following parameters: Synchronization Interval: the interval at which SMC automatically synchronizes incremental data to Alibaba Cloud. Maximum Reserved Images: the maximum number of images that can be retained during incremental data synchronization. SMC automatically synchronizes incremental data to Alibaba Cloud at the specified interval. For more information about the best practices for incremental data synchronization, see Migrate incremental data from a server. If you disable this feature, incremental data is not synchronized.	Keep the default setting
Enable Migration Template	If you set the Destination Type parameter to ECS Image, this parameter is available. The migration template is used to preset parameters for a migration task, and the template parameters are automatically filled in when the migration starts. For more information about setting up a migration template, see Configure the migration template.	Keep the default setting

Adjust the disk partition structure as needed. The following table describes the parameters.

Parameter

Description

Example

Modify Disk Partition

Determine whether to enable Modify Disk Partition based on your needs. This feature is only supported in SMC client 2.8.0 or above. For more information, see Use the SMC client.

Not enabled: By default, the disk partition structure of the destination system are the same as those of the migration source.
Enabled: You can adjust the destination disk partition structure, including partition size and order, transfer method, whether to enable LVM, and other configurations.
The parameter descriptions for the disk partition structure are as follows.
Configure disks
Configure mount targets
System Disk: the size of the system disk of the destination instance. Unit: GiB. Valid values: 20 to 2048,
The size of the destination system disk must be larger than the amount of data on the source system disk. For example, if the total size of the source system disk is 400 GiB but the size of data stored on this disk is only 100 GiB, you must set this parameter to a value greater than 100.
Note
The default value of this parameter is the size of the source system disk. We recommend that you retain the default value or specify a greater value.
Data Disk <N>: the size of the data disk of the destination instance. Unit: GiB. Valid values: 1 to 32768.
The variable <N> indicates the serial number of the data disk. If the disk is migrated to the destination instance, N is the ID of the data disk.
The size of the destination data disk must be larger than the amount of data on the source data disk. For example, if the total size of the source data disk is 500 GiB but the size of data stored on this disk is only 100 GiB, you must set this parameter to a value greater than 100.
If there are no mount targets under the data disk or if all mount targets are not migrated, the data disk will not be migrated.
LVM: Logical Volume Manager (LVM) is a mechanism for managing disk partitions in Linux systems. LVM is more flexible than traditional disk partitions and allows for dynamic adjustment of disk space.
You can select whether to enable LVM based on your needs. After enabling LVM, the destination will automatically rebuild the disk with an LVM structure.

Example description:

For each destination disk where LVM is enabled, the system will create one Physical Volume (PV) and its corresponding Volume Group (VG). On the VG, a number of Logical Volume Manager (LVM) corresponding to the mount targets are created. By default, the VG name is vgX (where X is the serial number of the disk), and the LVM name is lvX (where X is the serial number of the LVM). An example is provided in the following figure.

Important
LVM is not supported in the following scenarios:
When the migration source is a Windows system.
When the system disk does not have a boot partition.
After enabling LVM, the feature does not take effect in the following scenarios:
The migration source does not support lvm2 or the lvm2 package is not installed.
The migration source is a Debian system with a kernel version of 3.x or earlier, and disks with XFS file systems are mounted.
Whether to Migrate: You can select whether to migrate the mount target based on your business needs.
Enable Block Replication: Enabling block replication can effectively improve the stability of migration transmission speed while ensuring consistency with the source partition structure. However, the partition size cannot be modified. SMC determines whether to support enabling block replication based on the migration source disk partition status.
If the migration source does not support block replication for partitions, the Enable Block Replication switch cannot be turned on, and default file replication method is used, allowing partition size modification.
If the migration source supports block replication for partitions, the Enable Block Replication switch is enabled by default to achieve partition-level disk migration.
Note
When the migration source is a Windows operating system, the block replication feature is enabled by default and cannot be disabled.
If LVM is enabled on the disk and the partition size is not an integer multiple of 4 MiB, block replication does not take effect, and file replication is used for data transfer.
Set partition size: When block replication is not enabled, you can set the partition size based on your needs, but the sum of partition sizes cannot exceed the size of the disk they belong to.
Note
If the size of disks of the destination instance do not match that of the migration source disks, the migration task cannot be created. In this case, the system will automatically adjust the mount target positions to meet the disk size requirements. If the requirements cannot be met after the adjustment, handle the issue as prompted.
You can also manually drag and drop mount targets to meet disk size requirements. However, drag-and-drop is not supported for partitions of type boot or system. The specific operations are as follows:
Move your pointer over before the mount target.
Use your pointer to drag the mount target to another disk.

Keep the default setting

Conditionally required. Click Advanced Settings to configure advanced parameters such as network type, private network IP address, and transmission speed limit. The following table describes the parameters.

Parameter	Description	Example
Network Type	The type of network that is used to migrate data from the source server to the intermediate instance. By default, data is migrated over the Internet. During the migration, SMC creates an intermediate instance that connects to a vSwitch in a VPC. If you select Public Network, a public IP address is assigned to the intermediate instance. Public Network (default value) VPC SMC migrates data to the intermediate instance over the Internet. If you select Public Network, make sure that the source server can access the Internet. You can determine whether to specify a VPC and a vSwitch based on your business requirements. If you specify a VPC and a vSwitch, SMC creates an intermediate instance that connects to the specified VPC and vSwitch. If you do not specify a VPC or vSwitch, SMC creates an intermediate instance that connects to the VPC and vSwitch automatically created by the system. SMC migrates data to the intermediate instance over a VPC. If you select VPC, you must specify a VPC and a vSwitch and make sure that the source server can connect to the VPC. Note If your server in a data center, your VM, or your third-party cloud server can connect to a VPC, we recommend that you select this network type to migrate data. Compared with migration over the Internet, migration over a VPC is more efficient and stable. You can use VPN Gateway, Express Connect, or SAG to connect a migration source to a VPC. For more information, see Connect a data center to a VPC.	Keep the default setting
Private IPv4 Address	If you need to change the private IP address of the destination instance, you can manually specify the private IP address. This parameter appears only when the Destination Type is selected as ECS Instance. Remain Unchanged: The default value is the IP address of the destination instance after migration and does not change. Manually Specify: You are allowed to enter an address within the available IP CIDR block of the vSwitch where the destination instance is located. When the migration source IP address is in the CIDR block of the vSwitch, you can change the destination instance IP address to the migration source IP address. When the CIDR block of the destination instance is the same as that of the migration source: Enter the private IP address of the migration source. When the CIDR block of the destination instance is different from that of the migration source: Change the VPC of an ECS instance to make the CIDR block of the destination instance the same as that of the migration source, and then enter the private IP address of the source.
Transmission Speed Limit	The maximum network transfer speed during the migration. Unit: Mbit/s. If you set the Compression Ratio parameter to a value greater than 0, the actual network transfer speed, which is the transfer speed of compressed data, is lower than the speed displayed in the Real-time Migration Status column.	Keep the default setting
Compression Ratio	The compression ratio of the data to be migrated. Set the compression ratio based on your business requirements. If the bandwidth is limited, a high compression ratio improves the transmission efficiency. If a high bandwidth is available, we recommend that you do not compress data. Data compression consumes CPU resources of the migration source. Valid values: 0 to 10. Default value: 7. A value of 0 indicates that data is not compressed.	Keep the default setting
Checksum Verification	Specifies whether to verify data integrity by using a checksum. By default, this feature is disabled. If you enable this feature, data integrity is ensured, but transmission speed may be reduced.	Keep the default setting
License Type	The license type. Valid values: Alibaba Cloud (default): Only a Microsoft Windows Server license is supported. After migration, you are charged license fees for an image when you use the image to create an ECS instance, and the image is automatically activated. For more information, see the What Windows Server licenses does Alibaba Cloud support? section of the "FAQ" topic. BYOL: SMC allows you to bring your own license (BYOL). You can bring your own Microsoft license or register with Red Hat Enterprise Linux and SUSE Linux Enterprise Server. After migration, you are not charged license fees for an image when you use the image to create an ECS instance. You can use your own license for activation. Note If you have created an ECS instance, you can quickly purchase software licenses such as Red Hat Enterprise Linux and SUSE Linux Enterprise Server for specified ECS instances supported by Alibaba Cloud. For more information, see Purchase a software license for an ECS instance.	Keep the default setting
Image Check	Specifies whether to enable the image check feature. The image check feature checks whether an image is valid and whether the image can be used to create full-featured ECS instances. You can use the image check feature when you migrate servers or VMware VMs without agents. This feature helps you identify potential issues in images or ECS instances after the migration job is complete, and provides solutions to the identified issues. This helps you improve the success rate of starting ECS instances. For more information, see Configure image check.	Keep the default setting
Tag	The tags that you specify for the migration job. Each tag contains a key and a value. You can use tags to query and manage migration jobs. For more information, see Use tags to manage migration sources and migration jobs and Use tags to implement fine-grained access control. Note You can specify up to 20 tags for a migration job.	Keep the default setting
Intermediate Instance Type	The type of the intermediate instance. Select an intermediate instance type based on your business requirements. This parameter is available only if you set the Destination Type parameter to ECS Image. The instance type of the intermediate instance is automatically selected. If you specify an instance type, SMC creates an intermediate instance of the specified type. If the specified instance type is unavailable, the migration job fails to be created. If you do not specify an instance type, SMC automatically creates an intermediate instance. Important Do not stop, start, restart, or release the intermediate instance during the migration to prevent migration failures. After the migration is complete, SMC automatically releases the intermediate instance.	Keep the default setting

In the message that appears, read the migration notes and click Got It.
On the Server Migration page, view the real-time status of the migration job.
If you enable a migration test, SMC will first perform the test and proceed with the migration operation after the migration test is passed. The amount of time required for data transmission is subject to factors such as the data size of the migration source and network bandwidth. Wait until the migration job is complete.
Note
- Speed: the amount of data that is migrated per second, which indicates the transfer speed of uncompressed data. If you set the Compression Ratio parameter to a value greater than 0, the actual network transfer speed, which is the transfer speed of compressed data, is lower than the displayed speed.
- Time Remaining for Synchronization: the remaining synchronization time calculated based on the current speed by using the following formula: Time remaining for synchronization = (Total data size - Transferred data size)/Speed.
- If the transmission speed is too slow to meet your plan, you may consider temporarily increasing the dedicated bandwidth of both the source server and the destination server. For more information, see Estimate the time required for migration and test the data transfer speed.
For details about how to subscribe to SMC migration job error-related events and modify and pause the migration job, perform the following operations.
- To prevent migration process disruptions caused by errors in migration jobs, you can subscribe to SMC migration job error-related events in CloudMonitor so that you can promptly receive email notifications. For more information, see Subscribe to SMC migration task error-related event notifications.
- When the migration job is in the Synchronizing state, you can perform the following operations as needed:
  Modify the migration job: In the Actions column, click Modify Migration Job to modify the Transmission Speed Limit, Compression Ratio, and Checksum Verification parameters.
  Pause the migration job: In the Actions column, click Pause Migration Job.
Optional. To view details about the migration, perform the following steps:

View migration details

In the Migration Source ID /Name column of the destination migration source, click the migration source ID to view the job details.

Verify the migration result

If Completed is displayed in the Real-time Migration Status column, the migration is successful.
- If you set the Destination Type parameter to ECS Image for the migration job, you can verify the migration result in the following way:
  After the migration is complete, an Alibaba Cloud custom image is generated. You can use your pointer to slide the scrollbar at the bottom to the right and click View Report in the Migration Deliverables column to view the check result of the image. For more information, see View the image check results step of the "Configure image check" topic.
  (Recommended) Manually verify the migration result
  Use the automatic migration result verification feature
  
  You can click Create Instance in the Actions column to go to the ECS instance creation page in the ECS console. The custom ECS image created by the migration job is selected by default for you to create an ECS instance. For more information, see Create an instance by using a custom image.
  Note
  To use this feature, you must install the Cloud Assistant Agent in your instance, and the system version of the instance must support this feature. For more information, see Install Cloud Assistant Agent.
  This feature uses the ACS-SMC-CreateAndVerifyInstance template provided by Alibaba Cloud CloudOps Orchestration Service (OOS) to automatically verify whether the image generated by the migration job can be used to create an ECS instance and whether the ECS instance can start as expected.
  Click Verify Migration Result in the Actions column.
  In the dialog box that appears, read the instructions on the verification process and click Verify Now.
  You can also click Customize Verification Parameters to configure the parameters.
  In the Verify Migration Result column, view the verification result. Valid values:
  Verified: indicates that the migration is successful. You can click Details to check the verification result.
  Not Verified: indicates that the migration failed. You can click View Cause to troubleshoot the failure.
  You can also click the icon in the Actions column and select View Verification Records in OOS Console to view the template history.
- If you set the Destination Type parameter to ECS Instance for the migration job, you can click View Destination Instance in the Actions column to go to the details page of the destination ECS instance to verify the migration result.
After the server is migrated, you must perform the following operations to ensure normal operation of your business:
- Verify the integrity and correctness of the data. For more information, see the How do I check my system after I migrate a Linux server? or How do I check my system after I migrate a Windows server? section of the "FAQ" topic.
- Manually start the applications and services after the migration if automatic start is not enabled for the applications and services on the source server.
- The IP address changes after the migration job is complete. If the service involves the configuration of the IP address, modify the domain name resolution and ICP filing after the migration.
  If a domain name has been bound to the source server, the public IP address of the server is changed after the migration. In this case, you must resolve the domain name to the new public IP address of the server. For more information, see Add an A record for a website domain name.
  If you want to keep the private IP address unchanged, you can modify the private IP address after the migration is complete.
  Migrate a server to an ECS Image: Modify the private IP address when creating an ECS instance. For more information, see Specify the primary private IPv4 address when creating an ECS instance.
  Migrate a server to a Destination Instance: If you have not modified the IPv4 private network address in the advanced configuration of the Migration Settings step, you can also modify the IPv4 private network address after migration. For more information, see Change the primary private IPv4 address for an existing ECS instance.
If the migration test is in the state, the migration test failed.

In this case, you need to check the test report, fix the test items that are in the Critical state, and then perform a test again. For more information, see Configure a migration test.
If Error is displayed in the Real-time Migration Status column, the migration failed.
In this case, you need to perform the following operations:
1. Click Troubleshoot Errors in the Actions column and fix the failure based on the error code and error message. For more information, see FAQ about Server Migration Center (SMC) and Errors occurred during a server migration.
2. In the migration source list, click Retry Migration Job.
  The migration job resumes from the point where it was suspended.
  Important
  If the intermediate instance is released, you must create another migration job. For more information, see the What do I do if I release an intermediate instance by accident? section of the "FAQ" topic.

Clear resources

Migrate a server to an ECS image
During the migration, SMC creates a temporary pay-as-you-go intermediate instance named No_Delete_SMC_Transition_Instance within the destination Alibaba Cloud account. The method to clear resources depends on whether the migration is successful.
- If the migration is successful, the intermediate instance is automatically released. No manual operation is required.
- If the migration failed, the intermediate instance is not automatically released and incurs fees as long as the migration job exists. You can release the intermediate instance in one of the following ways to reduce costs:
  - If you no longer need the migration job, click the ID the migration job. On the job details page, click > Clear migration task in the Actions column in the Migration Jobs section to delete the migration job and release the intermediate instance at a time.
  - Manually release the intermediate instance. For more information, see Release an instance.
Migrate a server to an ECS instance
During the migration, SMC creates a temporary pay-as-you-go intermediate cloud disk named SMC_Temp_Disk in the destination instance. The method to clear resources depends on whether the migration is successful.
- If the migration is successful, the intermediate cloud disk is automatically released. No manual operation is required.
- If the migration failed, the intermediate cloud disk is not automatically released and incurs fees as long as the migration job exists. You can release the intermediate cloud disk in one of the following ways to reduce costs:
  - If you no longer need the migration job, click the ID of the migration job. On the job details page, click > Clear migration task in the Actions column in the Migration Jobs section to delete the migration job and release the intermediate cloud disk at a time.
  - Manually release the intermediate instance. For more information, see Release a disk.

Relevant references

If you need to migrate incremental data multiple times, you can initiate incremental data migration multiple times at custom intervals after the first full migration is complete. This synchronizes the incremental data generated by the source server to Alibaba Cloud and reduces the suspension time and delivery time of the services provided by the source server. For more information, see Migrate incremental data from a server.
For more information about frequently asked questions (FAQ) and solutions, see FAQ about Server Migration Center (SMC) and Errors occurred during a server migration.

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