Share data by using CSG to attach OSS buckets to ECS instances - Object Storage Service

To allow multiple users to access data in an Object Storage Service (OSS) bucket in different locations by using different devices as they access local files, you can use Cloud Storage Gateway (CSG) to attach the OSS bucket to an Elastic Compute Service (ECS) instance and then map the bucket to a local directory. This way, you can manage OSS objects in the same manner as you manage local files and share objects.

Prerequisites

CSG is activated and is granted access permissions on OSS, ECS, and Virtual Private Cloud (VPC). To activate CSG, go to the CSG console.
The bucket that you want to attach to an ECS instance must be located in one of the following regions: China (Hangzhou), China (Shanghai), China (Qingdao), China (Beijing), China (Zhangjiakou), China (Hohhot), China (Ulanqab), China (Shenzhen), China (Heyuan), China (Chengdu), China (Hong Kong), Singapore, Malaysia (Kuala Lumpur), Indonesia (Jakarta), Japan (Tokyo), Germany (Frankfurt), US (Silicon Valley), and US (Virginia).
A VPC and a vSwitch are created in the same region in which the bucket that you want to attach is located. For more information, see Create and manage a VPC and Create and manage a vSwitch.
An ECS instance is created in the same region in which the bucket that you want to attach is located. For more information about how to create an ECS instance, see Create and manage an ECS instance by using the ECS console (express version).

Usage notes

We recommend that you do not upload Archive, Cold Archive, and Deep Cold Archive objects to buckets after you attach the buckets to ECS instances by using CSG.
When you upload objects to buckets that you attached to ECS instances by using CSG, CSG calls the CopyObject operation to modify the object metadata to configure the last modified time of the objects. Archive, Cold Archive, or Deep Cold Archive objects need to be restored during the CopyObject operation, which is time-consuming and affects the upload efficiency. In addition, objects may fail to be uploaded because data in the cache disk is not uploaded in a timely manner. If you do not need to modify an object for a long period of time after it is uploaded, you can set its storage class to Standard or infrequent access (IA), upload the object, and then change its storage class to Archive, Cold Archive, or Deep Cold Archive by configuring lifecycle rules. For more information, see Lifecycle rules based on the last modified time.
When you access OSS by using CSG, you are charged based on the specifications, cache type, and public bandwidth of the gateway. You are also charged storage fees and API operation calling fees. For more information, see Billing.

Step 1: Configure CSG

Log on to the OSS console.
In the left-side navigation pane, click Buckets. On the Buckets page, find and click the desired bucket.
In the left-side navigation tree, choose Object Management > Attach OSS Bucket to ECS. On the page that appears, click Configure Gateway.

In the Basic Information step of the Create Gateway dialog box, configure the following parameters and click Next.

Parameter	Description
Edition	Select the specification of the gateway. This depends on the capacity of the bucket that you want to attach and the bandwidth required for data transmission between the bucket and the ECS instance. For example, if 10 million or fewer objects are stored in the bucket, the capacity of the bucket does not exceed 64 TB, and the required bandwidth does not exceed 1 Gbit/s, you can select Basic. For more information, see File gateways.
VPC	Select the VPC in which the ECS instance to which you want to attach the bucket resides.
VSwitch	Select the vSwitch in the VPC where the ECS instance to which the bucket you want to attach resides.

In the Config Protocol step, configure the following parameters and click Next.

Parameter	Description
Name	Enter the name of the gateway that you want to create. The name can be up to 60 characters in length and can contain letters, digits, `periods (.), underscores (_), and hyphens (-)`. It must start with a letter.
Subdirectory	If you want to use CSG to attach a subdirectory of a bucket as a file system to an ECS instance, select Subdirectory next to Bucket Name and enter the subdirectory name.
Protocol	Select the protocol used by the file gateway. NFS: applicable to Linux systems. SMB: applicable to Windows systems.
Share Name	Specify the name of the network share used to access the attached bucket. The network share name can contain only letters, digits, `periods (.), underscores (_), and hyphens (-)`. The name must start with a letter. The name can be up to 32 characters in length.
User Mapping	Specify the user that is used to access the attached bucket from an NFS client. This parameter can be configured only when Protocol Type is set to NFS. Valid values: none: All users on the NFS client are directly used to access the attached bucket. root_squash: The root user on the NFS client is mapped to the nfsnobody user on the NFS server to access the attached bucket. all_squash and all_anonymous: All users on the NFS client are mapped to the nfsnobody user on the NFS server to access the attached bucket. After the bucket is attached to the ECS instance by using CSG, all users have read, write, and execute permissions on objects in the bucket. You can configure User Mapping in one of the following ways based on your requirements: If you want to manage access permissions on objects in the attached bucket, set User Mapping to none and then manage the access permissions as the root user. For more information, see Step 3: (Optional) Configure access permissions on objects. If you do not need to manage access permissions on objects in the attached bucket, set User Mapping to a value except none.
Reverse Sync	Select whether to synchronize the metadata of objects in the attached bucket to the cache disk of the gateway. If you set Reverse Sync to Yes, data consistency between the gateway and the OSS bucket is ensured. If you set Reverse Sync to Yes, you need to specify Reverse Sync Interval. Important Reverse Sync Interval specifies the interval at which two consecutive reverse synchronization tasks are run. Valid values: [15, 36000]. Unit: seconds. If you set Reverse Sync to Yes, the performance of the cache disk may be downgraded. We recommend that you do not set Reverse Sync Interval to a value smaller than 300. If you enable Reverse Sync, all objects in the attached bucket are scanned, and you are charged API operation calling fees. For more information, see API operation calling fees.
Cache Disk Type	Select the type of the cache disks. Valid values: Ultra Disk, Standard SSD, and ESSD Cloud Disk PL1. The supported cache disk types may vary based on the region where the ECS instance resides. Select a cache disk type based on your business requirements.
Cache Capacity	Select the capacity of the data cache. Unit: GB. Valid values: [100, 32768]. To ensure data access performance, CSG reserves storage space in the ECS instance equivalent to the size specified in this parameter to cache hot data.

In the Billing Information step, select Cloud Storage Gateway Service Agreement and "The OSS service is independent of the CSG service. If you delete the OSS bucket, the gateway associated with the bucket will not be released. If you no longer use the gateway, go to CSG Console to release the gateway.", and then click Finish.
By default, a pay-as-you-go gateway is created. You can change the billing method of the gateway to subscription, which is more cost-effective. For more information, see Switch the billing method from pay-as-you-go to subscription.

Step 2: Attach and access the bucket

After you purchase the gateway, you can attach the bucket to the ECS instance. In the following steps, a file gateway that uses the NFS protocol is used to attach the bucket. To use a gateway that uses the SMB protocol to attach the bucket, see Access an SMB share.

In the left-side navigation tree, choose Object Management > Attach OSS Bucket to ECS.
In the gateway list, check the value in the Server Mount Target column that corresponds to the gateway that you want to use.
Log on to the ECS instance to which you want to attach the bucket. The ECS instance runs the Linux system and is in the same region as the gateway.
For more information, see Connect to an instance by using VNC.
Run an NFS command to attach the bucket to the ECS instance.
For example, if the value of Server Mount Target is 172.16.0.2:/test and the local path to which the bucket is attached is mnt/nfs/, you can run the following command to attach the bucket to the ECS instance:
```
mount.nfs 172.16.0.2:/test /mnt/nfs/
```
Access the attached bucket.
The following examples show how to use an NFS command to access the attached bucket: Examples:
- Run the following command to list the objects in the root directory of the mounted bucket:
```
ls mnt/nfs/
```
- Run the following command to download an object named example.txt from the root directory of the attached bucket to the local root directory:
```
cp mnt/nfs/example.txt  example.txt
```

Step 3: (Optional) Configure access permissions on objects

Log on to the NFS client as the root user.
Configure access permissions on objects in the attached bucket.
For example, you can perform the following steps to grant read-only permissions on an object named example.txt to the nfsnobody user. By default, the UID and GID of the nfsnobody user are both 429496****.
1. Run the following command to change the user group associated with example.txt to the nfsnobody user group:
```
chgrp -R 429496**** example.txt
```
2. Run the following command to grant read-only permissions on example.txt to the nfsnobody user group:
```
chmod  444 example.txt
```
Optional. Change the value of User Mapping.
After you configure access permissions on objects in the attached bucket, we recommend that you change the value of User Mapping to root_squash, all_squash, or all_anomnymous to limit the permissions of the root user.
1. Log on to the .
2. In the left-side navigation pane, click Gateways. Then, click the gateway that is used to attach the bucket to the ECS instance.
3. Click Settings in the Actions column of the gateway.
4. In the NFS Share Settings dialog box, modify the value of User Mapping based on your requirements.
5. Click OK.

FAQ

What is the difference between attaching OSS by using CSG and attaching OSS by using ossfs?

The performance of attaching OSS by using CSG is better than attaching OSS by using ossfs. ossfs is not suitable for high concurrency and the upload and download of large objects. ossfs is suitable for managing small objects. For more information, see ossfs.

Is a gateway released if I delete buckets attached by using the gateway?

No, the gateway is not released. If you no longer need to use the gateway, go to the CSG console and delete it in a timely manner to prevent unnecessary fees.