VMware:- VM Snapshot Process

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A snapshot preserves the state and data of a virtual machine at a specific point in time.

--> The state includes the virtual machine’s power state (for example, powered-on, powered-off, suspended).

--> The data includes all of the files that make up the virtual machine. This includes disks, memory, and other devices, such as virtual network interface cards.

Snapshot With :

Memory: If the flag is 1 or true, a dump of the internal state of the virtual machine is included in the snapshot. Memory snapshots take longer to create, but allow reversion to a running virtual machine state as it was when the snapshot was taken. This option is selected by default.

Note: When taking a memory snapshot, the entire state of the virtual machine will be stunned.

Quiesce: If the flag is 1 or true, and the virtual machine is powered on when the snapshot is taken, VMware Tools is used to quiesce the file system in the virtual machine. Quiescing a file system is a process of bringing the on-disk data of a physical or virtual computer into a state suitable for backups.

Snapshot Files:

-.vmdk and --delta.vmdk : A collection of .vmdk and -delta.vmdk files for each virtual disk is connected to the virtual machine at the time of the snapshot. These files can be referred to as child disks or delta links.

If the virtual disk is larger than 2TB in size, the delta file is of --sesparse.vmdk format

.vmsd    : The .vmsd file is a database of the virtual machine's snapshot information and the primary source of information for the Snapshot Manager .

Snapshot.vmsn :  The .vmsn file includes the current configuration and optionally the active state of the virtual machine. Capturing the memory state of the virtual machine lets you revert to a turned on virtual machine state. With nonmemory snapshots.

This diagram is an example of a snapshot Disk chain:

Snapshot Best practice :

---> VMware recommends only 32 as the maximum number of snapshots can take.

---> Avoide taking snapshot for SQL/Active Directory domain servers(time sensitive application servers).

---> VMware does not recommend manually modifying the disk chain as it may result in data loss.

---> Snapshot should not run more than 3 days or longer it will leads Performance issues or permanent data loss.

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