Tuesday, October 16, 2018

VMware Snapshot and Snapshot Manager

You can use the Snapshot option to make a copy of the virtual machine's disk file (VMDK) at any time. This option gives you the ability to roll back your VM at any given point to the date that you created the snapshot. Snapshot is helpful if you made changes to the system that cause an unexpected error or if your VM is unable to boot. Snapshots alone do not provide backup

Any data that was writable on a VM becomes read-only when the snapshot is taken. VMware administrators can take multiple snapshots of a VM to create multiple possible point-in-time restore points. When a VM reverts to a snapshot, current disk and memory states are deleted and the snapshot becomes the new parent snapshot for that VM. The snapshot file cannot exceed the size of the original disk file, and it requires some overhead disk space. Snapshots will grow rapidly with high disk-write activity volume. Most snapshots are deleted within an hour and VMware recommends deleting snapshots within 24 hours. 

Snapshot file formats include *--delta.vmdk file, *.vmsd file and *.vmsn file. Administrators create snapshots in VMware vSphere's Snapshot Manager or with the vmware-cmd command line utility. Deleting, or committing, snapshots merges all of the delta files into the VMDK. If delta files remain in the VM's directory after deletion, the snapshot did not delete properly.

VMware recommends the following best practices regarding snapshots:

Do not keep a single snapshot for more than 72 hours. While VMware supports up to 32 snapshots in a chain, try to limit chains to three snapshots. 

Do not rely upon snapshots for I/O intensive VMs with rapid data changes, because significant data inconsistencies will occur when the VM is restored.

Snapshot Manager

You can use the Snapshot Manager to perform the following tasks

1. Show AutoProtect snapshots in the Snapshot menu
2. Prevent an AutoProtect snapshot from being deleted
3. Rename a snapshot or change its description
4. Delete a snapshot


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