Help Center/ Server Migration Service/ Service Overview/ Precautions
Updated on 2025-09-03 GMT+08:00
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Precautions

Pre-Migration

  • You need to check the OS version of the server you are migrating. If it is too early, for instance, Windows Server 2008, the kernel may be incompatible and services on the server may fail to start after the migration is complete. To avoid this issue, you need to evaluate whether a lift-and-shift migration is suitable for the server before the migration.
  • You need to disable any software such as antivirus or security software that may prevent the SMS Agent from start on the server. If you are not sure whether there is a software conflict with the Agent, back up your data before the migration.
  • Linux block-level migration is in the open beta test (OBT) and is only recommended for testing scenarios.
  • The VirtIO drivers must be installed in the source server OS, or the target server may fail to start after the migration is complete. If your source server runs on Huawei Cloud, you can install the drivers by referring to Installing VirtIO Drivers.
  • There are differences between the source and target servers after the migration. For details, see What Are the Differences Between the Source and Target Servers After the Migration?

Migration Network

  • Before using SMS, you need to set up a secure network. For details about the network requirements, see How Do I Set Up a Secure Migration Network for Using SMS?
  • You need to correctly configure security group rules for the target server by referring to How Do I Configure Security Group Rules for Target Servers?
  • The migration occupies some source server resources, such as memory, CPU, disk I/O, and bandwidth. You can limit the resource allocation for the migration. If the source server runs Linux, Traffic Control (TC) must be installed and run properly on it. Otherwise, traffic limiting may not be applied.

Migration Duration

  • The migration speed is affected by factors such as network bandwidth, disk I/O, CPU and memory usage, and file size and quantity, so it is impossible to accurately estimate the migration duration. The remaining migration duration estimated by SMS for a migration task is for reference only. For more information, see Migration Duration.
  • It is recommended that data migration and service cutover be completed within 30 days.
  • The time required for an incremental synchronization is affected by many factors, such as the number of incremental files, the continuity of valid blocks, and the size of incremental data. It is impossible for SMS to estimate the required time.

In-Migration

  • Before a migration is complete, do not perform operations on the OS or disks of the target server, including but not limited to changing or reinstalling the OS.
  • Make sure you have backed up any data on the target server that you need to save and ensure that the disks can be formatted. Disks on the target server will be formatted and re-partitioned based on the source disk settings during the migration.
  • During the migration of a Windows source server, do not restart the source server. The restart will disconnect the source server from the SMS console. To retry the migration, you need to delete the migration task and create a new one.
  • Do not restart the Agent during a Windows migration or a Linux block-level migration.
  • You are advised not to start the Agent during a Linux file-level migration unless necessary, even though resumable data transfer is supported.
  • During the migration, a temporary pay-per-use disk is created and attached to the target server to ensure that the migration runs normally. After the migration is complete, the disk is automatically detached and deleted. If you manually delete the migration task before it completes, you need to manually delete the temporary disk to avoid extra fees.
  • If an error occurs during the migration, you are advised to provide migration logs to technical support engineers so that the fault can be resolved quickly.

    For details about how to get migration logs, see Where Can I Find the Agent Run Logs?

Post-Migration

  • SMS migrates OS and data. It ensures data consistency before and after the migration, but does not ensure that your applications will run properly on the target server after the migration is complete. You may need to adjust your applications by yourself.
  • SMS gives you the capability to verify data consistency before and after the migration. You can enable verification when you configure the target server or initiate an incremental synchronization. Note that consistency verification cannot be performed for servers with Btrfs file systems.

Target Server Modifications

After the full migration of a Linux server, some parameter settings in the directories below on the target server are modified to make the target server compatible with Huawei Cloud and ensure that the target server can start properly. During incremental synchronization, data in these directories is not synchronized by default to prevent parameter settings in these directories on the target server from being overwritten or modified.

/proc/*,
/sys/*,
/lost+found/*,
/tmp/_MEI*,
/var/lib/ntp/proc/*,
/boot/*,
/boot/efi/*,
/etc/fstab,
/etc/*,
/etc/X11/*,
/root/initrd_bak/*,
/lib/modules/*,
/boot/grub2/x86_64-efi/*,
/boot/grub2/i386-pc/*

Requirements for Linux Migration Rate Limiting

To limit the migration speed for a Linux source server, the tc command and cbq kernel module must be installed on the source server.

  • To check whether the tc command is installed, run the following command on the Linux terminal. If the system returns the tc function list, the tc command has been installed. 
    # tc
  • To check whether the cbq module is installed, run the following command on the Linux terminal. If the system returns the related information, the cbq module is loaded. 
     lsmod | grep sch_cbq