In general, a Snapshot denotes a photograph of an object. In the technology perspective, a snapshot is an informative image which consist data of a system. In the same way when we talk about VMware snapshot, a snapshot is a one which consists the state and data of a virtual machine at a specific point of time. The state of the VM signifies the VM’s power state i.e Power On, Power Off, Suspended. The data of the VM signifies the data that makes the virtual machine which includes all the attributes related to the VM like disks, memory, any attached devices and network interface cards.
VMware virtual machines provides several options to work with snapshot like creating a snapshot, managing the snapshot like revert to any snapshot in the chain and deleting the snapshots. Let us discuss how to work with vmware virtual machine snapshots.
Creating a Snapshot
1→ Right click on the virtual machine that you want take snapshot
2→ Select Snapshot option from the menu pops up and select Take Snapshot from the sub menu
3→ Then there will be a dialog box appears with options to take snapshots
4→ Enter the Name and Description that makes the snapshot as identical
5→ Below the description panel there will be two checkbox available as
a) Snapshot the virtual machine’s memory
b) Quiesce guest file system(Needs VMware Tools installed)
Note: When the virtual machine is in power on state then by default the first option would be selected. If both these options are not selected, then the snapshot process will create files that are crash consistent and could be used to reboot the VM.
a) Snapshot the virtual machine’s memory
Usually memory snapshot takes longer to accomplish since it’s taking a dump of the virtual machine’s internal state. Memory snapshot allows to revert the running state as it was in the state while taking the snapshot.
b) Quiesce guest file system(Needs VMware Tools installed)
To perform this snapshot, the VMware tools must be installed in the virtual machine since the VMware tools is used to quiesce the file system of the virtual machine. Quiescing a file system is a process of making the on disk data of a VM to a state which is suitable for backups. This process might include such operations as flushing dirty buffers from the operating system’s in-memory cache to disk, or other higher-level application-specific tasks.
Note: The Quiescing process is essential only when there is a backup need since the backup data should be in the state of consistent and be usable during recovery. Quiescing indicates pausing or altering the state of running processes on a computer, particularly those that might modify information stored on disk during a backup.
The Snapshot is comprised of the below files
- <vm>-<number>.vmdk and <vm>-<number>-delta.vmdk
- <vm>.vmsd
- <vm>Snapshot<number>.vmsn
Vembu VMBackup uses the quiesce method of snapshot to backup the Virtual Machines to make sure the backup data are recoverable and crash consistent during recovery which also comprised with application aware process if enabled during the backup configuration to make sure consistency of high end applications like Exchange Server, SQL Server.
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