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Recover data from damaged or formatted VMFS disks or VMDK files
Recover data from damaged or formatted VMFS disks or VMDK files

What is a VMware snapshot?

Here you will find out:

  • what is a virtual machine snapshot
  • how does it work
  • when DiskInternals can help you

Are you ready? Let's read!

Virtual machine snapshot

A snapshot of a virtual machine is a copy of all the settings, configurations, and files in a VM at a given moment.

At any time, you can create a new snapshot of the VM or roll back to one of the previous ones.

If snapshots are taken successively, they form a chain, and if rollbacks are made to snapshots, a tree will form.

You can create snapshots, restore VMs from snapshots, and delete snapshots.

What files are created with snapshot in VMware?

A virtual machine snapshot is stored in three files with the following extensions:

  • delta.vmdk and flat.vmdk
  • .vmsd
  • snapshot.vmsn

More details:

  • .vmdk and -delta.vmdk are child files, which can later become parent files for future child files. If the size of the virtual disk exceeds 2 TB, -delta.vmdk has the format --sesparse.vmdk. The names of these files are selected depending on the presence of the file name and may not match.
  • .vmsd is a so-called virtual machine snapshot database. All information for the snapshot manager is stored here (row records that determine the relationship between snapshots, child disks for each snapshot).
  • snapshot.vmsn is the file that has configuration data and, if necessary, VM status (this allows you to return to the prior state of the virtual machine).

Note: -delta.vmdk files and snapshot descriptor files are in the same place as virtual disks.

VMware Workstation snapshot: what is inside?

VMware snapshot files contain the following information:

  • Configuration for the virtual machine
  • The current state of all virtual machine disks
  • The contents of the virtual machine memory

There are situations when you need to remove one of the snapshots; some special-purpose configurations require this. To do this, in the "Edit" tab, select "Virtual Machine Settings". Next, in the Advanced section, click “Independent”.

Click on one of these options:

  • Intermittent: changes will stop after turning off the VM
  • Permanent: changes will be on an ongoing basis

How to take snapshots in VMware

If everything is done correctly, you can save a certain state of the VMware VM and restore it when needed (for example, if the VM fails).

Therefore, pay attention to how to take a snapshot in VMware:

Decide on the settings:

  1. 1. Name: defines the file
  1. 2. Description: gives a description of the snapshot
  1. 3. Memory: creating snapshots of memory requires additional time; but it means you can return to the prior state of the virtual machine. Usually, this function is turned on automatically. During the snapshot making process, the VM memory will be unavailable.
  1. 4. Quiesce: when creating a snapshot, the file system is paused so that it is convenient to back up, clear dirty buffers from the RAM cache on disk, etc.

Why do VMware snapshot files matter?

If you have a snapshot, there is a chance to restore the VM in case of failure, so that you can access all the necessary data and configurations. So this is a great way to get the state of the virtual machine that you need at the moment.

Be careful: If the snapshot manager creates snapshots, it may erroneously indicate that there are no snapshots. But actually this is not so: during a snapshot, the record is deleted from the snapshot manager configuration file and then it just does not see the snapshot.

Three examples of VMware Workstation snapshot usage

The uses of snapshots can be illustrated by these examples:

  • If the snapshot function is not needed, then it is better to turn on the VM without a snapshot; this will increase productivity. You can make sure that you don’t have a snapshot as follows: click on the “Snapshot” button and select the “Delete snapshot” button.
  • If you started any experiments with VMs (software testing, etc.), then it's time to take a snapshot so as not to lose all the information and current state of the VM. It should be understood that when you create a new snapshot, you lose the previous snapshot.
  • If you want your VM to boot at a certain state (i.e. each VM start was from a particular snapshot), you can do this by changing some settings. This is done as follows: in the "Editing" section, click on "Virtual Machine Settings". Here, click on the “Snapshot” tab and in the “When turning off the power” section, click on the “Return to Snapshot” button. When you want the virtual machine to be paused at startup, pause the virtual machine before saving the snapshot.

How to revert to a snapshot?

There are various photos to pick from in the diagram below. The VM will be operating if we rollback to a snapshot with a green icon.

  1. 1. To revert to a snapshot, select one from the snapshot manager (for example, Patch 2) and click Revert To.
  1. 2. Click OK.
  1. 3. Keep in mind that unless you preserve the present state of the virtual machine in a snapshot, you'll lose it. This implies that any changes you make to the VM that are not recorded by producing a snapshot will be lost. Click OK when you're ready to go on.
  1. 4. The snapshot management screen will show you where in the snapshot tree you are. Click You'll have to manually start the VM because the Patch 2 snapshot lacks the machine's RAM.

VMware snapshot best practices

Because VM snapshots take up a lot of space, you should only have 2 or 3 of them.

Snapshots are good for test and development VMs, but not for production VMs. Because you are double IOPS and there is CPU cost in determining the block-level difference, a VM with snapshots generally has poor performance. The performance deterioration is determined by the length of time the snapshot or snapshot tree has been in use, the depth of the tree, and how much the VM and its guest operating system (OS) have changed since the snapshot was taken.

As previously stated, snapshots are not intended to be used for backup and recovery. In your datacenter, always utilize a good backup software solution.

Only individual VM snapshots may be detected by Snapshot Manager. There are third-party solutions that allow you to monitor and manage snapshots for many VMs, giving you more control over your virtual environment. You can, for example, instantly detect and analyze unlawful snapshot generation or deletion throughout your virtual environment.

How to restore snapshots with DiskInternals VMFS Recovery

DiskInternals VMFS Recovery restores VMDK snapshots on VMware vSphere servers and ESXi/ESX. In addition, this tool automatically checks the current status of the RAID (if used), VMware VMFS data storage, and drives. You will also receive a free preview of absolutely all files found.

Only then will you be asked to purchase a license and export files to local or remote locations (including FTP).

Instructions for using VMFS Recovery:

Download DiskInternals VMFS Recovery and install it.

  1. 1. Connect via SSH if necessary.
  1. 2. Open the disk (via SSH or local disk).
  1. 3. Perform a scan and find the necessary VMDK files after it.
  1. 4. Next, mount the VMDK file.
  1. 5. Browse for free the files that the program found and make sure they are intact.
  1. 6. Purchase a license and obtain a license key to complete the export of data.

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