Cloud host snapshot is a replica for the cloud host state at a specific time. You can save cloud host settings and disk data for cloud host data restoration and recovery. Before operating system upgrade, application software installation, or application software upgrade for a cloud host, you can create a snapshot for the cloud host. If the system cracks because of the previous operations or the software fails to run correctly, you can fast restore the cloud host through the snapshot. To periodically create snapshots for a cloud host, you can create a snapshot policy. For more information, see "Manage snapshot policies."
Cloud host snapshots include external snapshots and internal snapshots. Internal snapshots are stored in the disk files. External snapshots are used for storing incremental data through creating incremental disks. You can use both snapshot types at the same time. If the cloud host has an internal snapshot created, you can only create internal snapshots afterwards. Similarly, if the cloud host has an external snapshot created, you can only create external snapshots afterwards.
Creating an internal snapshot will set the assigned cluster in the current disk to read-only and mark the cluster as being used by a snapshot. When a new write IO request is received to edit a cluster, copy the cluster data and create a new cluster. Consequent modifications will be saved to the new cluster. Because the internal snapshot for the cloud host is saved to the basic disk file, a damage to or deletion of the file will also delete the snapshot data. Deleting the internal snapshot can release disk space. To avoid excessive disk file size, as a best practice, control the number of snapshots by deleting unnecessary cloud host snapshots to release the disk space.
Creating an external snapshot will set the current disk to read-only, and enable the system to create incremental image file in the storage path of the disk. Consequent modifications to the disk data will be saved to the incremental image file. Creating a snapshot for the disk again will set the original disk and the current incremental image file to read-only and enable the system to create another incremental image file in the data storage, forming an image chain with data dependencies. Because the external snapshot saves incremental data through creating incremental image files, it has relatively low impact on the cloud host services, and is suitable for cloud hosts with frequent service changes.
Deleting an external snapshot will not change the cloud host or other snapshots. Deleting the snapshot will combine images by writing the incremental image files after the snapshot to the upper-level image files. To avoid excessive number of snapshots to generate a long image chain that affects cloud host performance, as a best practice, control the number of snapshots by deleting some of them.
If the cloud host image experiences multiple external snapshot and restoration operations, redundant incremental image files might exist. For example, after deleting an external snapshot, the associated incremental image file might not be combined to the upper-level image. Excessive redundant incremental image files will affect cloud host performance. By simplifying the image chain through combining images in it, you can reduce the number of image chain levels for faster disk read speed. Simplifying the image chain will combine incremental image files to the upper-level images without affecting data dependencies.
The maximum number of virtualization automatic snapshots is 1000. The maximum number of host snapshots is 1000.
The cloud host snapshot quota settings and the upper snapshot limit in snapshot policies for organizations are independent from each other. An upper-level organization cannot assign those quotas to a lower-level organization.
You can only increase cloud host snapshot quotas.
In organization quota management, the maximum quota setting for host snapshots is 1000. The upper limit for the automatic snapshot quota must be less than the host snapshots.
When adding a cloud host to the host snapshot policy, if the cloud host has no host snapshots or has external snapshots, an external snapshot is automatically created. If the cloud host has internal snapshots or is attached with RBD storage, an internal snapshot is automatically created.
When creating a cloud host snapshot or restore the cloud host through snapshot, avoid modifying the cloud host configuration. If you modify the cloud host configuration, you might fail to restore the cloud host through snapshot.
When creating a snapshot for the cloud host, the CPU configuration is not specified in the snapshot. The CPU configuration of the cloud host will not be affected by snapshot restoration.
If you attach the cloud disk or vNIC or edit the flavor settings after creating a cloud host snapshot, restoring the snapshot might result in inconsistency with cloud-end configuration.
Creating cloud host snapshots and snapshot policies requires using specific CAS versions. For more information, see Key Features and Software Platforms Compatibility Matrix.
On the top navigation bar, click Cloud Services, and then select Cloud Hosts from the Compute menu.
Click More for the target cloud host, and then click Create Snapshot.
Specify the parameters.
Table-1 Creating a snapshot
|
Parameter |
Description |
|
Creation Mode |
Specify the creation mode, Manual or Auto. If you select Manual, you can select a snapshot policy for the cloud host. |
|
Snapshot Type |
Select External Snapshot or Internal Snapshot. Internal snapshots are stored in the disk files. External snapshots are used for storing incremental data through creating incremental disks. If the cloud host has an internal snapshot created, you can only create internal snapshots afterwards. Similarly, if the cloud host has an external snapshot created, you can only create external snapshots afterwards. |
|
Memory Snapshot |
Specify whether to take a snapshot for the cloud host memory. The default setting is No. When the cloud host memory usage is too high, taking snapshot for the memory might suspend services on the cloud host. This parameter is available only when the collaborated CAS version supports memory snapshot. If the CAS version does not support memory snapshot, you will create a normal snapshot even if you select memory snapshot. |
Click OK
On the top navigation bar, click Cloud Services, and then select Cloud Hosts from the Compute menu.
Click the name of the target cloud host.
Click the Snapshots tab.
Select the target snapshot and view its details in the Snapshot Details area.
On the top navigation bar, click Cloud Services, and then select Cloud Hosts from the Compute menu.
Click the name of the target cloud host.
Click the Snapshots tab.
Select the target snapshot and click Modify.
Edit the parameters and then click OK.
If you restore a snapshot for a cloud host with a NIC mounted, the NIC will be rolled back. If you restore a snapshot for a cloud host after editing its flavor, the flavor settings will be restored. If you attach a data disk and then restore the snapshot, the data disk will be lost.
To restore a snapshot:
On the top navigation bar, click Cloud Services, and then select Cloud Hosts from the Compute menu.
Click the name of the target cloud host.
Click the Snapshots tab.
Select the target snapshot and click Restore.
Click OK.
On the top navigation bar, click Cloud Services, and then select Cloud Hosts from the Compute menu.
Click the name of the target cloud host.
Click the Snapshots tab.
Select the target snapshot and click Delete.