{{ $t('productDocDetail.updateTime') }}: 2025-12-18

1. Virtual machine snapshots are not intended as a backup method; they are only used to protect virtual machines before high-risk operations such as virtual machine patch upgrades and software updates.

2. For clusters with three or more hosts using aSAN virtual storage, storage snapshots (based on storage-level Redirect-on-Write (ROW) technology) are used by default to take snapshots of virtual machines. If a virtual machine has existing snapshots created on an older version of the platform, you can choose either "Continue using virtual disk snapshots" or "Switch to storage snapshots". When switching to storage snapshots, you need to clear all previously created virtual disk snapshots.

3. When using external storage, virtual disk snapshots (based on qemu’s ROW technology) are used to take snapshots of virtual machines.

4. For two-host clusters using aSAN virtual storage, virtual disk snapshots are used by default, and storage snapshots are not available. When the cluster is scaled up to three hosts, you can switch to storage snapshots (on the premise that all previously created virtual disk snapshots need to be cleared first).

5. The maximum number of storage snapshots supported is 48.

6. Taking a virtual machine snapshot will interrupt services, with an interruption time ≤ 1 second.

7. When quiescing is enabled in a snapshot policy, if the virtual machine does not support quiescing or quiescing fails, a non-quiesced snapshot will be created.

8. Quiescing supports file system consistency (requiring the file system format to be NTFS) and application consistency (but requires support from the application itself).

9. Quiescing a virtual machine during snapshot creation has a certain impact on services, so it should be enabled with caution.

10. External snapshots, internal snapshots, and storage snapshots cannot coexist; a virtual machine can only have one type of snapshot at a time.

11. For virtual machines in a hyper-converged infrastructure that has been upgraded to version 6.10.0 and already have internal snapshots, internal snapshots will be created by default when new snapshots are taken.

12. For new virtual machines or virtual machines without existing snapshots, external snapshots will be created by default when disk snapshots are taken.

13. Deleting snapshots outside the fork point involves merging multiple snapshot chains. Since each snapshot contains incremental changes to the base disk, merging multiple snapshot chains may result in a large number of data merging operations, which have a negative impact on system performance. Therefore, deleting snapshots outside the fork point is not supported.

14. Deleting an external snapshot takes longer than deleting an internal snapshot. This is because external snapshots include incremental changes made to the base disk and index information of these incremental changes. When deleting an external snapshot, these incremental changes need to be merged into the base disk to restore the state before the snapshot was deleted, and this merging process can be very time-consuming.

15. To ensure the normal operation of the quiescing function, users need to ensure that the Windows system services relied on by quiescing are functioning properly. If these services are not enabled, the creation of quiesced snapshots will fail:

    - The COM+ System Application service must be "Running", and its startup type must be set to "Manual".

    - The COM+ Event System service must be "Running", and its startup type must be set to "Automatic".

    - The Volume Shadow Copy service must not be in a running state, and its startup type must be set to "Manual".

16. When memory snapshot is enabled, the virtual machine’s services will be interrupted during the snapshot saving process. It is recommended to perform this operation during off-peak business hours. The interruption time is related to the memory configuration size and IO load (for example, a virtual machine with 32 cores and 64GB of memory may be affected for 10 minutes under high load conditions).

17. The memory snapshot feature cannot be used in the following scenarios:

    - Virtual machines that have not installed the performance optimization tool or have installed the tool but not restarted to make it effective, cannot use the memory snapshot feature.

    - Virtual machines in scenarios such as USB mapping, GPU passthrough, physical disk mounting, and encryption card configuration cannot use the memory snapshot feature.

    - Virtual machines in a powered-off state cannot use the memory snapshot feature.

    - Virtual machines with the escape prevention feature enabled cannot use the memory snapshot feature.