File Storage NAS:Migrate data by using Robocopy

When to use this method

How it works

Robocopy creates mirror copies of directory structures, preserving file attributes and timestamps. The tool skips duplicate files, making it efficient for incremental synchronization.

Billing

Data migration incurs the following costs:

Step 1: Prepare the environment

Ensure the ECS instance can access both file systems.

1. Get the mount target information of the source file system.

2. Configure the destination file system based on your scenario:

   Scenario	Action
   Same VPC	Proceed to Step 2: Create an ECS instance.
   Different VPCs in the same region	Create a mount target for the destination file system, then use CEN to connect the VPCs.
   Different accounts or regions	Use CEN to connect the VPCs.

Step 2: Create an ECS instance

Important: Create a dedicated ECS instance for data migration. Using an existing instance may consume CPU and network bandwidth allocated to running workloads.

1. Log on to the ECS console and click Create Instance.

2. Configure the following parameters:

   Parameter	Configuration
   Region	Select the region where the source file system resides.
   Network and Zone	Select the VPC, zone, and vSwitch of the source file system.
   Instance	For migrations under 100 GB, select the minimum specification. For migrations over 1 TB, select at least 8 vCPUs and 16 GiB memory.
   Image	Select Windows Server 2019 for optimal compatibility.
   Storage	Click Elastic Ephemeral Disk | NAS File System | Dedicated Block Storage Cluster(Optional), then click Add File System.

   If you use Windows Server 2025, disable SMB signing before mounting NAS file systems. Run the following command in PowerShell as an administrator, then restart the instance:

   reg add "HKLM\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters" /v RequireSecuritySignature /t REG_DWORD /d 0 /f

Step 3: Mount the file systems

1. Mount both the source and destination file systems to the ECS instance.

2. Verify the mount:

   net use

   Expected output:

   Status     Local      Remote                                                Network
   -------------------------------------------------------------------------------
   OK         Y:         \\29e9c24****-eab13.cn-hangzhou.nas.aliyuncs.com\myshare
                                                                              Microsoft Windows Network
   OK         Z:         \\29fe7f4****-txr31.cn-hangzhou.nas.aliyuncs.com\myshare
                                                                              Microsoft Windows Network

Step 4: Run Robocopy

Run the following command to migrate data from the source file system (Z:) to the destination file system (Y:):

robocopy Z:\ Y:\ /E /COPY:DAT /MT:8 /R:3 /W:5

Warning: Do not use /COPYALL for NAS-to-NAS migration. NAS SMB does not support full NTFS security attributes. Using /COPYALL causes the error: A required privilege is not held by the client.

Step 5: Verify the migration

Run the following command to verify data consistency:

robocopy Z:\ Y:\ /E /L /NS /NJS /NJH /NDL /FP /LOG:reconcile.txt

ECS instances

1. Run net use to obtain the mount information.

2. Unmount the original file system:

   net use Z: /delete

3. Mount the new file system to the original drive letter.

4. Restart processes that access the file system.

5. Update the auto_mount.bat file with the new mount target.

Windows containers

1. Modify the YAML configuration file with the new mount target.

2. Generate new pods with the modified configuration.

3. Recycle all pods that use the original file system.

Important: Retain data in the original file system for at least one week after switching workloads. Immediate deletion may cause data loss from accidental deletion or synchronization.

How do I accelerate large-scale data migration?

For migrations involving hundreds of millions of small files (over 10 TB), use the Python-based parallel migration script:

1. Install the latest Python on the Windows ECS instance.

2. Set the PATH environment variable:

   set PATH=%PATH%;C:\python27

3. Copy the migration.py script to the ECS instance.

4. Run the migration:

   python ./migration.py -s Z:\ -d Y:\

For multi-client parallel migration, assign different subdirectory ranges to each client:

• Client 1: -r 0:9999

• Client 2: -r 10000:19999