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Virtual machine snapshots best practices in the vSphere environment (1025279)

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Purpose

This article provides best practices for virtual machine snapshots in the vSphere environment.

Resolution

Best practices to maintain snapshots on a virtual machine

  • Snapshots are not backups:

    • A snapshot file is only a change log of the original virtual disk and should not be retained as a backup.

  • Snapshots are not complete copies of the base vmdk disk files:

    • Taking a snapshot does not create a complete copy of the original virtual_machine-flat.vmdk disk file. It only creates a place holder disk to store data changes since snapshot is created.
    • The change log in the snapshot file combines with the original disk files to match with the current state of the virtual machine.
    • If the base disks are deleted, the snapshot files are not enough to restore a virtual machine.

  • The maximum supported amount of snapshots in a chain is 32 in the vCenter Server:

    • VMware recommends to use only 2-3 snapshots in a chain.
    • An excessive number of snapshot files in a chain can also impact virtual machine performance.

  • Do not use single snapshot for more than 24-72 hours:

  • Large snapshot files can cause reduced system performance:

    • Larger snapshots require more storage resources when deleting/committing them to the original virtual machine disks.
    • Virtual machines that are IO intensive. For example, email and database servers will have a higher snapshot growth rate.

  • Third party backup software:

    • Regularly monitor the virtual machines disks configured for backups to ensure that no snapshots remain after a successful backup.
    • Snapshots should only be present for the duration of the backup process.
    • Snapshots taken by third party software (called through API) may not show up in the vCenter Snapshot Manager. Routinely check for snapshots through the command-line. For more information, see Determining if a virtual machine is using snapshots (1004343).

  • Storage vMotion:

    • For vSphere 5.0 and previous versions, confirm that there are no snapshots present (through command line) before a Storage vMotion. If snapshots are present in the pre-vSphere 5.0 setting, delete the snapshots before the Storage vMotion.
    • vSphere 5.0 and later support Storage vMotion with snapshots present on a virtual machine. For more information, see Migrating virtual machines with snapshots (1035550).

  • Increasing the virtual machine disk size:

    • Confirm that there are no snapshots present before increasing the size of any virtual machine virtual disk or virtual RDM.
    • Increasing the size of a disk with snapshots present can lead to corruption of snapshots and a potential data loss. For more information, see Increasing the Size of a Virtual Disk (1004047).

Tags

fault/crash vm-snapshot-best-practices, vmware snapshot best practices,Error while consolidating VM disk with I/O errors,Unable to consolidate the disks

See Also

Update History

03/01/2012 - Added more information under the Best Practices topic. 10/24/2012 - Updated product ESXi 5.1.x 03/12/2015 - Added ESXi 5.5 and ESXi 6.0 to Products.

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