Error S6: Failed to create partition snapshot

Symptoms

A Server Migration Center (SMC) migration job fails and returns an error message such as "S6_* Failed to create a disk partition snapshot". Possible S6_* error codes include the following:

• S6_8

• S6_1

Causes

During block replication, the SMC client automatically creates a snapshot device for a disk partition on the source server to synchronize data. This error occurs if the SMC client fails to create the snapshot. The causes vary depending on the source server's operating system:

• Windows:

  • Insufficient space on the disk partition.

  • Third-party security or antivirus software is installed.

  • The storage limit for Volume Shadow Copy is insufficient.

  • The Volume Shadow Copy Service is not working correctly.

• Linux

  • Insufficient space on the disk partition.

  • Available memory is less than 300 MB.

  • The snapshot device for the disk partition is not working correctly.

Solutions

The solution varies depending on the operating system of the source server:

• Windows

  Open Event Viewer and check for errors from sources such as vss, volsnap, or disk. Resolve the issues as indicated by the error messages.

  • If the error indicates insufficient disk space or that the VSS shadow copy cannot be extended:

    • Ensure the disk partition has enough free space. We recommend reserving at least 10% to 15% of the total space.

    • Check if the storage limit for Volume Shadow Copy is too small. Increase the limit or remove it, and then try again.

      Open the disk Properties dialog box, select the Shadow Copies tab, choose the target volume, and then click Settings.... In the Maximum size area, select No limit or increase the Use limit value (for example, to 4095 MB), and then click OK.

  • If an 'Access is denied' error occurs with the error code 0x80070005, check for third-party security or antivirus software. Grant the required disk backup permissions or temporarily disable the software, and then retry the operation.

  • Ensure the Volume Shadow Copy Service is running correctly.

• Linux

  1. Check if the /dev/smcss9 device exists, and run the dmesg | grep smcss command to check for related errors.

     1. Ensure the system has at least 300 MB of available memory.

     2. Ensure the disk partition has enough free space. We recommend reserving at least 10% to 15% of the total space.

     3. In the SMC client installation directory, run the ./Check/client_check --ssclear smcss command to clear any residual snapshot devices, and then try again. To find the SMC client installation directory, see View and run the SMC client.

  2. (Conditional) If the error message contains "io scheduler not support", change the disk's I/O scheduler by following these steps.

     1. Identify the index of the affected disk.

        Find the msg part of the error message. For example, in msg=CreateSnapshot 0-x Failed, 0-x indicates the first disk, 1-x indicates the second disk, and so on.

     2. Use the index from step i to find the corresponding disk device name.

        Run the lsblk command to identify the disk device name for the index. Indexes start from 0.

        [root@xxx ~]# lsblk
        NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
        vda    253:0    0    40G  0 disk              # Disk index 0
        ├─vda1 253:1    0     2M  0 part
        ├─vda2 253:2    0   200M  0 part /boot/efi
        └─vda3 253:3    0  39.8G  0 part /
        vdb    253:16   0   100G  0 disk              # Disk index 1
        └─vdb1 253:17   0   100G  0 part /data

     3. Use the disk name from step ii to check the disk's current I/O scheduler.

        For example, for disk vdb, run the cat /sys/block/vdb/queue/scheduler command to view its I/O scheduler.

        In the output, the scheduler in brackets ([]) is the current scheduler.

        mq-deadline kyber [bfq] none

        Note

        The output lists all available I/O schedulers: mq-deadline, kyber, bfq, and none.

     4. Replace the current scheduler (bfq) with a different scheduler.

        Use any scheduler other than bfq. For example, to switch to mq-deadline:

        Run the command sudo echo mq-deadline > /sys/block/vdb/queue/scheduler.

        Run the cat /sys/block/vdb/queue/scheduler command again to confirm the change. The output shows that the scheduler is changed from bfq to mq-deadline.

        sudo echo mq-deadline > /sys/block/vdb/queue/scheduler
        cat /sys/block/vdb/queue/scheduler
        [mq-deadline] kyber bfq none

After you resolve the network issue, run the SMC client to retry the operation. For more information, see Run the SMC client.