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Scale-down migration

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Scale down Cloud Disks by using Server Migration Center (SMC) to migrate an ECS instance to a custom image or a destination instance with smaller disks.

Migration limits

You cannot migrate ECS instances created from Alibaba Cloud Marketplace images. To use this feature, contact us to have your account added to the whitelist.

Migration impact

Before you start the migration, review the following potential impacts.

Affected item

Description

Migrated data directories

During the migration, you can adjust the partition structure of the destination disk, including partition size, order, transfer method, and Logical Volume Management (LVM) configurations.

By default, all of the server's disks are migrated:

  • If a data disk has no mount point, the data disk is not migrated.

  • If you do not need to migrate certain partition directories, you can deselect them when you adjust the partition structure.

Intermediate instance

Do not interfere with the intermediate instance.

To prevent migration failure, do not stop, start, restart, or release the intermediate instance, or change its billing method during the migration. SMC automatically releases the intermediate instance after the migration is complete.

Note

  • For each migration, SMC creates a temporary, pay-as-you-go intermediate instance named No_Delete_SMC_Transition_Instance in your destination Alibaba Cloud account to assist with the migration.

  • If you migrate to a destination instance, that instance serves as the intermediate instance and is not automatically released.

For more information, see How it works.

IP address

Migrating a server changes its IP address, which can interrupt services. We recommend performing the migration during off-peak hours. If your services involve IP address configurations, you must update the domain name resolution and ICP filing after the migration.

Underlying hardware

The migration changes the underlying hardware, which can invalidate application licenses bound to it. Check these licenses before you start.

Performance impact

The migration process consumes server resources, including CPU, memory, disk I/O, and network bandwidth.

Data consistency

For information about issues caused by data or system configuration changes during the migration, see Data consistency issues after migration.

Web application impacts

Migrating a server to Alibaba Cloud ECS changes several aspects of your environment. These include network topology, compute and storage resources, application security settings, cost, monitoring, compatibility, network latency and bandwidth, backup and recovery, and O&M processes. You must also consider the following:

Impact

Description

Network connectivity

After migration, the ECS instance resides in a new VPC. This changes its network location and configuration, preventing direct communication with your original network or other ECS instances in the source VPC. To enable cross-account and cross-VPC communication, see VPC interconnection.

Security group

The migrated ECS instance uses new security group rules to control inbound and outbound traffic. Changes to access rules may affect your services. If the destination security group lacks the required rules, export the rules from the source security group and import them into the destination security group. For more information, see Import and export security group rules.

SSL certificate

If your website uses HTTPS, apply for and install an SSL certificate. You can apply for a free SSL certificate from Alibaba Cloud and deploy it to the ECS instance. For more information, see Purchase and deploy an SSL certificate to an ECS instance.

Data migration

If you need to migrate data from other servers, you can use methods like FTP, SCP, or manual backups to OSS. For more information, see Transfer files to an ECS instance and Use ossutil to transfer data to an ECS instance.

Other configurations

Ensure that database connections, APIs, SLB, and other settings point to the new domain name and ECS IP address.

Prerequisites

  • You have completed the pre-migration preparations.

  • You have read the migration guide to learn about the SMC client, how migration works, billing, the migration process, and feedback channels.

  • To prevent data loss, back up important data to an image, a snapshot, or an external storage device before the migration.

  • If you migrate a server across international regions, the migration may be slow due to unstable public network connections. Evaluate the migration duration and test the transfer speed. Use VPN Gateway, Express Connect, a physical leased line, or Smart Access Gateway to connect the source server to an Alibaba Cloud Virtual Private Cloud (VPC) and perform the migration over a private network.

  • If you can directly access a Virtual Private Cloud (VPC) in a specific Alibaba Cloud region from your on-premises data center, virtual machine environment, or cloud server, use the private network migration solution. Private network migration is faster and more stable than migrating over the public network.

  • To migrate a source server to an existing ECS instance:

    • The operating system of the destination instance must match that of the source server (both must be Linux or both must be Windows).

    • The destination instance must have at least as many data disks as the source server. If the destination instance has an insufficient number of data disks, you must attach a data disk.

    • The capacity of the system disk and each data disk on the destination instance must be greater than or equal to the used space on the corresponding disk of the source server. If the destination instance has insufficient cloud disk capacity, you must resize a disk.

Migration procedure

Note

To migrate a Windows instance, you must compress the disk space before you import the migration source. Otherwise, you cannot reduce the disk capacity.

Step 1: Import a migration source

Console import

Important

  • The source ECS instance must have public network access.

  • The source server must be in the Running state, and the Cloud Assistant agent must be running correctly. For more information, see View the status of the Cloud Assistant agent and handle exceptions.

  • If you use a RAM user to import a migration source, you must manage RAM user permissions:

    • The AliyunECSReadOnlyAccess permission for read-only access to ECS.

    • The AliyunECSAssistantFullAccess permission for full management access to Cloud Assistant.

  1. Go to the SMC console - Scale-in Migration page.

  2. On the Shrunk Migration page, click Import Migration Source.

  3. Configure the parameters for the migration source, and then click Import.

    The import process takes 3 to 10 minutes.

    Parameter

    Description

    Migration Source Type

    ECS Instance.

    Import Method

    Select Import through Console.

    Authorize Server Migration Center (SMC) to remotely connect to the source server from the console and automatically import the migration source. The Cloud Assistant feature is automatically used during the import process. Do not interrupt or exit the process.

    Region

    Select the region where the source server is located.

    Instance

    Search for and select the ECS instances to migrate by instance ID, name, or IP address. You can import multiple instances at once.

    Tag (Optional)

    Add tags to the migration task to facilitate search and management. For more information, see Use tags to manage migration sources and migration tasks and Use tags for fine-grained permission management.

    You can add a maximum of 20 tags to a migration task.

    Resource Group (Optional)

    Assign the task to a resource group to manage resources by project, business unit, or other dimensions.

  4. On the Shrunk Migration page of the SMC console, view the status of the migration source in the Real-time Migration Status column.

    • A status of Migration SourceOnline indicates a successful import.

    • Any other status indicates that the import failed. Troubleshoot the issue and then re-import the migration source.

      • Troubleshoot the issue using the console's error message or the SMC client log files. The default installation directories are:

        • Windows servers: C:\smc.

        • Linux servers: /smc.

      • For information about common issues and solutions, see SMC FAQ and Troubleshoot errors.

Command-line import

If you cannot use the console import method, import the migration source from the command line instead.

Important

  • The source server must have public network access. If a firewall is configured for the source server, see SMC service domain names to obtain the required SMC domain names and ports and add them to the firewall's allowlist.

  • If your source server cannot access the public network or you want to use a private network to improve migration efficiency, see Private network-based migration.

  1. Go to the SMC console - Scale-in Migration page.

  2. On the Shrunk Migration page, click Import Migration Source.

  3. Follow the on-screen instructions to configure the parameters and copy the activation command.

    Parameter

    Description

    Migration Source Type

    ECS Instance

    Import Method

    Select Use CLI to Import Server.

    Generate an activation script and run it on the source server to import the migration source.

    Migration Source Quota

    The number of migration sources that can be activated by using the activation code. Valid values: 1 to 1,000. Default value: 200.

    Validity Period

    The validity period of the activation code in days. Valid values: 1 to 90. Default value: 90.

    Activation Code

    To generate an activation code, perform the following steps:

    1. Click Generate.

    2. Based on the operating system of the source server, click the Linux Shell or Windows PowerShell tab.

    3. Click Copy to copy the activation command.

  4. Log on to the source server. Then, with administrator privileges, paste and run the copied command to import the migration source.

    Linux source server

    1. Log on to the Linux server.

    2. Paste and run the copied command with administrator privileges to import the migration source.

      image.png

      A success message similar to Import Source Server [s-bp18x8751kgz2oyh****] Successfully! indicates that the migration source was imported.

    Windows source server

    1. Log on to the Windows server.

    2. Open Windows PowerShell with administrator privileges.

    3. Paste and run the copied command to import the migration source.

      image.png

      A success message similar to Import Source Server [s-bp19rlidl3mwuptc****] Successfully! indicates that the migration source was imported.

      If the command fails to run, see What do I do if I fail to import a Windows migration source by using a command?

  5. On the Shrunk Migration page of the SMC console, view the status of the migration source in the Real-time Migration Status column.

    • A status of Migration SourceOnline indicates a successful import.

    • Any other status indicates that the import failed. Troubleshoot the issue and then re-import the migration source.

      • Troubleshoot the issue using the console's error message or the SMC client log files. The default installation directories are:

        • Windows source servers: C:\smc.

        • Linux source servers: /smc.

      • For information about common issues and solutions, see SMC FAQ and Troubleshoot errors.

SMC client import

Important

  • You must run the client on the source server. By default, public network access is enabled. If a firewall is configured for the source server, see SMC service domain names to obtain the required SMC domain names and ports and add them to the firewall's allowlist.

  • If your source server cannot access the public network or you want to use a private network to improve migration efficiency, see Private network-based migration.

  1. Go to the SMC console - Scale-in Migration page.

  2. On the Shrunk Migration page, click Import Migration Source.

  3. On the Import Migration Source page, configure the following parameters.

    Parameter

    Description

    Migration Source Type

    ECS Instance

    Import Method

    Select Use Client to Import Server.

    You must manually download and install the SMC client on the source server.

    Description

    1. In the Description section, follow the prompts to download, install, and activate the appropriate SMC client based on the operating system (Linux or Windows) and architecture (32-bit or 64-bit) of the source server.

    2. Click Generate and copy the activation code.

      You need to enter the activation code when you install the client.

  4. Import the migration source.

    Important

    Do not close the SMC client during the migration. Closing it will disconnect the source server from the SMC console and cause the migration to fail.

    Windows source server

    1. Use a remote connection tool that supports file transfer (such as WinSCP) to upload the downloaded SMC client to the Windows source server.

    2. On the Windows source server, use the built-in decompression tool or a third-party tool to decompress the SMC client package.

    3. In the SMC client folder that matches your source server's system version, double-click the go2aliyun_client.exe application to run it.

      A prompt appears, requesting administrator privileges. Click OK.

    4. Obtain an activation code or an AccessKey pair.

      • (Recommended) Get an activation code: In the Description section of the SMC console, click Generate and copy the code.

      • Obtain an AccessKey pair: The AccessKey pair of an Alibaba Cloud account consists of an AccessKey ID and an AccessKey secret. If you have not created an AccessKey pair, create one first.

    5. As prompted, enter the values for access_access_token_id and access_token_code, and then press Enter.

      If a message similar to Import Source Server [s-bp18x8751kgz2oyh****] Successfully! is returned, the migration source is successfully imported.

    Linux source server

    1. Use a remote connection tool that supports file transfer (such as WinSCP) to upload the downloaded SMC client to the Linux source server.

    2. Remotely connect to the Linux source server and decompress the SMC client package.

      This example uses the Linux 64-bit General-purpose Edition. If you use a different version of the SMC client, replace the package name in the command with the name of the file that you downloaded.

      tar -zxvf go2aliyun_client.tar.gz
      Note

      The Linux 64-bit ARM Edition supports the g6r general-purpose and c6r compute-optimized instance families. For more information about instance families, see Enterprise-level Arm-based compute instance families.

    3. (Optional) Exclude files or directories that you do not want to migrate.

    4. Obtain an activation code or an AccessKey pair.

      • (Recommended) Get an activation code: In the Description section of the SMC console, click Generate and copy the code.

      • Obtain an AccessKey pair: The AccessKey pair of an Alibaba Cloud account consists of an AccessKey ID and an AccessKey secret. If you have not created an AccessKey pair, create one first.

    5. In the SMC client folder, run the following commands to start 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 entering an activation code: adad

      After you enter the activation code or AccessKey pair, the following prompts may appear:

      • If a snapshot driver is not installed on the source system, the SMC client displays the following prompt.

        Because block replication must be disabled for a scale-in migration of a Linux server, enter no.

        Important

        If the snapshot driver installation fails, do not enable block replication when creating the migration task, or the migration will fail.

        123

      • Most mainstream source systems have rsync installed by default. If rsync is not installed, the SMC client prompts you to install it. Enter yes to automatically install rsync.安装rsync

      • If SELinux is enabled on the source system, the SMC client prompts you to disable it. Enter yes to automatically disable SELinux.关闭SELinux

      If a message similar to Import Source Server [s-bp11npxndknsycqj****] Successfully! is returned, the migration source is successfully imported.

      Note

      If the import fails, troubleshoot the issue based on the error message. Then, run the following commands to exit the background process and re-import the migration source. For more information about common issues and solutions, see SMC FAQ and Troubleshoot errors.

      sudo ./go2aliyun_client --abort
sudo ./go2aliyun_client

  5. On the Shrunk Migration page of the SMC console, view the status of the migration source in the Real-time Migration Status column.

    • A status of Migration SourceOnline indicates a successful import.

    • Any other status indicates that the import failed. Troubleshoot the issue and then re-import the migration source.

      • Troubleshoot the issue using the console's error message or the SMC client log files. The default installation directories are:

        • Windows source servers: C:\smc.

        • Linux source servers: /smc.

      • For information about common issues and solutions, see SMC FAQ and Troubleshoot errors.

Step 2: Configure migration task

  1. In the Actions column of the target migration source, click Start Migration.

  2. Configure the parameters as instructed on the screen, and click Start Migration. In the confirmation dialog box, read the notes, select Got It, and then create the task.

    1. Configure basic parameters.

      Parameter

      Description

      Destination Type (Required)

      Select a destination type based on your migration scenario:

      ECS Image

      Converts the source server into a custom image that you can use to create a new ECS instance.

      The following parameters are available:

      • 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 prefix: The prefix of the custom image name after migration.

      ECS Instance

      Migrates the source server to an existing ECS instance. The source server and destination instance must have compatible storage and operating system configurations.

      Important

      Migrating to a destination instance replaces its operating system. The automatic snapshots of the system disk are deleted and cannot be restored. To keep automatic snapshots for data security or future use, you can prevent automatic snapshots from being released with their disks before the migration.

      The following parameters are available:

      • Destination Region: The Alibaba Cloud region to which you want to migrate your source server. This parameter is required. For more information about regions, see Regions and zones.

      • Destination Instance: Select an ECS instance as the destination instance.

      Automatic Incremental Synchronization

      Automatically synchronizes incremental data from the source server to Alibaba Cloud when enabled. Disabled by default.

      • If you enable this feature, you must configure the following parameters:

        • Synchronization Interval: The interval at which the incremental migration task is automatically run.

        • Maximum Reserved Images: The maximum number of images that are retained by default for the incremental migration task.

        The migration task is automatically run on a schedule to synchronize incremental data to Alibaba Cloud. For information about best practices for incremental migration, see Incremental server migration.

      • If you disable this feature, the migration task runs only once.

      Enable a migration template

      This parameter is available only when Destination Type is set to ECS Image.

      A migration template is used to pre-configure the parameters of a migration task. When you start the migration, the template parameters are automatically populated. For more information about how to configure a migration template, see Configure a migration template.

      Network Type

      Select the network for transferring data to the intermediate instance. By default, data is transferred over the public network, and the intermediate instance is created in the selected VPC and vSwitch with an automatically assigned public IP address.

      Public Network

      Data is transferred to the intermediate instance over the public network. To use this mode, the source server must have public network access. You can specify a VPC and a vSwitch based on your business requirements.

      • Specify VPC and vSwitch: The migration task creates an intermediate instance in the VPC and vSwitch that you specify.

      • Do not specify VPC and vSwitch: The migration task creates an intermediate instance in a new VPC and vSwitch that are automatically created by the system.

      VPC

      Data is transferred to the intermediate instance over a VPC. To use this mode, you must connect the source server to an Alibaba Cloud VPC and specify a VPC and a vSwitch.

      Note

      If you can directly access an Alibaba Cloud VPC in a specific region from an on-premises data center (IDC), a virtual machine environment, or another cloud host, we recommend that you use this migration method. Transferring data over a private network is faster and more stable than over the public network. You can use VPN Gateway, Express Connect, or Smart Access Gateway to connect the source server to the VPC. For more information, see Connect a VPC to a local data center or another cloud.

      The private IPv4 address of the destination instance

      This parameter is available only when Destination Type is set to ECS Instance.

      • Remain unchanged.: By default, the IP address of the Destination Instance is retained.

      • Manual: Allows you to enter an IP address from the available IP address range of the vSwitch to which the Destination Instance belongs. If the IP address of the migration source is within the CIDR block of the vSwitch, you can change the IP address of the destination instance to that of the migration source.

        • If 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.

        • If the CIDR block of the destination instance is different from that of the migration source: You must first change the VPC of the destination instance to make the CIDR blocks the same. Then, enter the private IP address of the migration source.

    2. Adjust the disk partition structure as required.

      Parameter

      Description

      Modify Disk Partition

      This feature is enabled by default and requires SMC client V2.8.0 or later. For more information about the SMC client, see SMC client usage guide.

      Linux systems

      Block replication is disabled by default. You can modify the disk size and partition sizes to configure a scale-in migration.

      • The destination disk size must be larger than the used capacity of the source disk.

        For example, if the source disk size is 60 GiB and the used capacity is 30 GiB, the destination disk size must be larger than 30 GiB.

      • The destination disk size must be larger than the sum of all partition sizes.

        For example, if the destination disk size is 40 GiB, the sum of all partition sizes must be less than 40 GiB.

      For information about other parameters, see Disk partition structure parameters.

      Windows systems

      Block replication is enabled by default and cannot be modified. The custom disk size must be larger than the sum of all partition sizes.

      Important

      Make sure that you have compressed the disk space for the migration source before you import it. Otherwise, you cannot reduce the disk capacity.

      For information about other parameters, see Disk partition structure parameters.

      The following table describes the parameters related to the disk partition structure.

      Configure disks

      By default, the destination disk partition structure is the same as that of the source disk.

      • System Disk: the size of the system disk for the destination ECS instance in GiB. Valid values: 20 to 2,048.

        The capacity of the destination system disk must be larger than the used capacity of the source system disk. For example, if the source system disk is 400 GiB in size and has 100 GiB of used capacity, the size of the destination system disk must be larger than 100 GiB.

        Note

        By default, this parameter is set to the size of the source system disk.

      • Data Disk <N>: the size of the data disk for the destination ECS instance in GiB. Valid values: 1 to 32,768.

        • The variable <N> specifies the data disk number. If you migrate the server to a destination instance, N is the data disk ID.

        • The size of the data disk must be larger than the used capacity of the source data disk.

        • If no mount point is available on a Data Disk or all mount points are set to not be migrated, the data disk is not migrated.

      • LVM: You cannot enable LVM for scale-in migrations.

        Logical Volume Manager (LVM) is a mechanism for managing disk partitions in Linux systems. LVM is more flexible than standard disk partitioning and allows you to dynamically adjust disk space.

      Configure mount points

      • Migrate: You can select whether to migrate data disks based on your business requirements.

      • Enable block replication: This option is visible only for SMC client versions earlier than 3.2.0. Using block replication can improve the stability of data transfer and ensure that the destination partition structure is consistent with the source. However, the partition size cannot be modified. SMC determines whether to enable block replication based on the partition status of the source disks.

        • If the source server runs Windows, block replication is enabled by default and cannot be disabled.

        • If the source server runs Linux, block replication is disabled by default and cannot be modified.

        • 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. File replication is used for data transfer.

      • Set partition size: If block replication is disabled, you can set the partition size as needed. The sum of the partition sizes cannot be greater than the size of the disk to which they belong.

      Note

      If the disk sizes of the destination instance do not match the source disks, the task cannot be created. In this case, the system automatically adjusts the positions of the mount points to meet the disk size requirements. If the requirements are still not met after the mount points are adjusted, troubleshoot the issue based on the on-screen message.

      You can also manually drag the mount points to meet the disk size requirements. However, you cannot drag boot partitions or system partitions. To do this, perform the following steps:

      1. Hover over the image icon next to the mount point.

      2. Drag the mount point to another disk.

    3. (Optional) To configure parameters such as migration drills, data transfer limits, compression ratio, and licenses, click Advanced Settings.

      Parameter

      Description

      Migration Job Name

      The name of the migration task.

      Job Description

      A description for the migration task.

      Migration Test

      A migration drill validates the task's feasibility and identifies risks before the actual migration, reporting data volume, migration speed, and estimated duration. Pay-as-you-go resources used during the drill are billed. By default, Migration Test is enabled.

      Warning

      If the destination type is ECS Instance, snapshots are created for all disks of the destination ECS instance during the migration drill. If the drill is abnormal or the execution mode is set to Test Only, the snapshots are automatically rolled back after the drill is complete. The destination ECS instance is unavailable during the migration drill, and the data on the instance is lost. Make sure that no important data exists on the destination ECS instance.

      For more information, see Configure a migration drill.

      Execution Method

      Select an execution mode based on whether Migration Test is enabled:

      Drill enabled

      • Test Only: Creates only a migration drill task. After the drill is complete, you must manually start the server migration task.

      • Test and Migrate: After the drill completes, the migration task starts automatically if there are no Critical issues. By default, Test and Migrate is selected.

      Drill disabled

      • Migrate Now: Starts the migration immediately after the task is created. By default, Migrate Now is selected.

      • Migrate Later: Starts the migration task automatically at a specified time after the task is created.

        The earliest scheduled execution time is 10 minutes after the current time.

      • Create Only: Creates only a migration task. You must manually start the task by clicking Run in the Actions column.

      Transmission Speed Limit

      The maximum speed at which data is transferred over the network, in Mbit/s. If Compression Ratio is set to a value greater than 0, the actual transfer speed will be lower than the speed shown in the Real-time Migration Status column.

      Compression Ratio

      Set the compression ratio based on your requirements.

      • In environments with limited bandwidth, a higher compression ratio can increase the data transfer speed.

      • In high-bandwidth environments, we recommend that you do not compress data to reduce CPU resource consumption on the migration source.

      Valid values: 0 to 10. Default value: 7. A value of 0 indicates that data is not compressed during transfer.

      Checksum Verification

      This feature is disabled by default. If you enable it, data consistency checks are enhanced, but the transfer speed may decrease.

      SSL Encrypted Transmission

      This feature is enabled by default to secure data in transit with SSL encryption.

      License Type

      • Alibaba Cloud (Default): Currently, only Microsoft Windows Server licenses are provided. After migration, license fees are charged when you create an ECS instance from the image in a region in China (Hong Kong) or outside the Chinese mainland. The operating system is automatically activated. The actual fees are displayed when you create the instance.

      • BYOL (BYOL): BYOL migration to the cloud is available for Microsoft, Red Hat Enterprise Linux, and SUSE Linux Enterprise Server. After migration, no license fees are charged when you create an ECS instance from the image. You must use your own license for activation.

        Note

        If you have already created an ECS instance, Alibaba Cloud allows you to quickly purchase software licenses, such as Red Hat Enterprise Linux and SUSE Linux Enterprise Server, for a specified ECS instance. For more information, see Purchase a software license for an ECS instance.

      Tag

      Add tags to the migration task to facilitate search and management. For more information, see Use tags to manage migration sources and migration tasks and Use tags for fine-grained permission management.

      Note

      You can add a maximum of 20 tags to a migration task.

      Intermediate Instance Type

      This parameter is available only when Destination Type is set to ECS Image.

      • Select an intermediate instance type: If you select a specific instance type, the system uses that instance type to create the intermediate instance. If the instance type is out of stock, the migration task fails to be created.

      • Do not select an intermediate instance type: The system selects an instance type from a predefined list to create the intermediate instance.

      Important

      To prevent migration errors, do not stop, start, restart, or release the intermediate instance during the migration. After the migration is complete, the instance is automatically released.

      Report diagnostic logs

      Automatically uploads SMC client logs to the SMC server for diagnostic analysis. This helps troubleshoot issues if a migration error occurs. This feature is enabled by default.

      SMC client logs are typically saved in the /smc/go2aliyun_client*/Logs directory within the installation directory.

  3. On the Server Migration page, view the real-time migration status.

    If you enabled migration drills, SMC performs a drill first. The data transfer duration depends on factors such as data volume and network bandwidth.

    image

    Note

    • Speed: The amount of data transferred per second before compression. If you set the Compression Ratio to a value greater than 0 when you create the migration task, the displayed speed is higher than the actual transfer speed of the compressed data.

    • Time Remaining for Synchronization: The estimated time until the synchronization is complete, calculated by using the following formula: (Total data volume - Transferred data volume) / Speed.

    • If the transfer speed is too low for your plan, consider temporarily increasing the fixed bandwidth of the source and destination servers. For more information, see Evaluate migration time and test transfer speed.

    Subscribe to migration error events, and modify or pause a migration

    • To be notified of migration errors, you can subscribe to SMC migration task error event notifications in CloudMonitor to receive timely SMS and email notifications.

    • While the migration task is in the Synchronizing state, you can also perform the following operations:

      • Edit a migration task: In the Actions column, click Modify Migration Job to modify parameters such as the data transfer limit, compression ratio, and checksum verification.

      • Pause a migration task: In the Actions column, click Pause Migration Job to pause the migration.

  4. (Optional) View migration details.

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

Verify the migration result

  • A Real-time Migration Status of Completed indicates that the migration was successful.

    • If the Destination Type is ECS Image:

      After a successful migration, a custom image is created in your Alibaba Cloud account. Scroll to the right and, in the Migration Deliverables column, click View Report to view the image detection results.

      Manual verification (Recommended)

      In the Actions column, click Create Instance. You will be redirected to the ECS instance creation page in the console, with the newly created custom image selected by default. For more information about how to create an ECS instance, see Create an instance from a custom image or a shared image. The default system disk type and capacity may not match the type and size of the scaled-down cloud disk. Adjust the settings as needed.

      image

      Automatic verification

      Note

      To use this feature, you must meet the following conditions:

      • During verification, a temporary pay-as-you-go instance is created from the custom image. Make sure that your Alibaba Cloud account has a balance of at least CNY 100.

      • You must install the Cloud Assistant agent on the instance. The instance must run a supported operating system version. For more information, see Install the Cloud Assistant agent.

      This feature uses the Alibaba Cloud OOS template ACS-SMC-CreateAndVerifyInstance to automatically create an ECS instance from the image and verify that it starts correctly.

      1. In the Actions column, click Verify Migration Result.

        image

      2. In the dialog box that appears, review the verification process and click Verify Now.

        You can also click Customize Verification Parameters to manually configure verification parameters.

      3. In the Verify Migration Result column, check the result.

        • Verified: The verification was successful. Click View Report to view more information.

        • Not Verified: The verification failed. Click View Cause to identify and troubleshoot the cause of the failure.

        You can also click the ... icon in the Actions column and select View Verification Records in OOS Console to view the OOS template's execution history.

    • If the Destination Type is ECS Instance, you can click View Destination Instance in the Actions column to open the destination ECS instance page.

  • If the migration drill status is image.png, the migration drill failed.

    Review the drill report, resolve all Critical drill items, and then retry the migration drill. For more information, see Configure a migration drill.

  • If the Real-time Migration Status is InError, the migration task has failed.

    In this case, troubleshoot the issue and retry the migration:

    1. In the Actions column, click Troubleshoot Errors. Use the provided error code and message to resolve the issue. For more information, see SMC FAQ and Troubleshoot errors.

    2. After fixing the issue, in the Actions column, click Retry Migration Job. The migration resumes from the point of failure.

      Important

      If you release the intermediate instance, you must restart the migration. For more information, see What do I do if I accidentally release an intermediate instance?.

Next steps

After a successful migration, follow these steps to ensure your business operates as expected:

Clean up resources

Migrate to an image

During the migration, SMC creates a temporary pay-as-you-go intermediate instance named No_Delete_SMC_Transition_Instance in your destination Alibaba Cloud account to assist with the migration. The outcome of the migration determines whether you need to manually release the instance:

  • Successful migration: SMC automatically releases the intermediate instance. No manual cleanup is required.

  • Migration error: SMC does not release the intermediate instance, which continues to incur charges. To avoid unnecessary charges, you can release the instance in one of the following ways:

    • If you no longer need the migration task, click the migration source ID. In the Actions column for the migration task, click Cancel Migration Job to delete the migration task and automatically release the intermediate instance.

    • Manually release the intermediate instance.

Migrate to an instance

During the migration, SMC creates a temporary pay-as-you-go intermediate disk named SMC_Temp_Disk and attaches it to the destination instance to assist with the migration. The outcome of the migration determines whether you need to manually release the intermediate disk:

  • Successful migration: SMC automatically releases the intermediate disk. No manual cleanup is required.

  • Migration error: SMC does not release the intermediate disk, which continues to incur charges. To avoid unnecessary charges, you can release the disk in one of the following ways:

    • If you no longer need the migration task, click the migration source ID. In the Actions column for the migration task, click Cancel Migration Job to delete the migration task and automatically release the intermediate disk.

    • Manually release the intermediate disk.

References

  • After the initial full migration, you can run incremental migrations at custom intervals to synchronize data from the source server and reduce downtime during the final cutover. For more information, see Incremental server migration.

  • To transfer an ECS instance to another Alibaba Cloud account and retain its public IP address, see Transfer an ECS server.

  • For solutions to common issues, see FAQ and Troubleshooting.

FAQ

How do I shrink a Windows disk?

This example demonstrates shrinking a data disk on Windows Server 2016. Adapt the steps to your environment.

Important

To prevent data loss, back up important data to an image, a snapshot, or a storage device separate from the instance before you proceed.

  1. Remotely connect to the server.

  2. On the Windows Server desktop, right-click the 开始图标 icon, and then click Disk Management.

  3. In the Disk Management dialog box, select Action > Rescan Disks to view the disk partitions and capacity.

    As shown in the following figure, Disk 0 (C drive) is the system disk and Disk 1 (D drive) is the data disk.

    image

  4. Right-click the volume that you want to shrink, and then click Shrink Volume.

    image

  5. In the Shrink D dialog box, enter a value for Enter the Amount of Space to Shrink in MB, and then click Shrink.

    Note

    • Enter the Amount of Space to Shrink in MB: Specifies the amount of unallocated space to create. By default, this field shows the maximum available shrink space. You can adjust this value.

    • Total Size After Shrink in MB: The final size of the partition (Drive D in this example) after shrinking.

    Enter the Amount of Space to Shrink in MB + Total Size After Shrink in MB = Total Size Before Shrink in MB. For example, 200000 MB + 107070 MB = 307070 MB.

    image

    After the operation completes, Disk 1 has 200,000 MB (195.31 GB) of Unallocated capacity.

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