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Performance impact when using VMware snapshots

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Using vmware and snapshots? You probably know about vmware best practices about snapshots, which includes

  • The maximum supported amount of snapshots in a chain is 32. However, VMware recommends that you use only 2-3 snapshots in a chain.
  • Use no single snapshot for more than 24-72 hours. Snapshots should not be maintained over long periods of time for application or Virtual Machine version control purposes.
  • An excessive number of delta files in a chain (caused by an excessive number of snapshots) or large delta files may cause decreased virtual machine and host performance.
  • Be especially diligent with snapshot use on high-transaction virtual machines such as email and database servers

But what is real performance inpact of snapshot?


I have found this older but very interesting article by Erik Zandboer – Performance impact when using VMware snapshots.

Some very important things can be extracted from this: For starters, the simple fact of having a snapshot to a VM means that all ROPS of this VM grow with a factor 2 (!). On top of that, when the VM writes a block that was not written to the snapshot before you also need twice the WOPS on that VM. This is due to the fact that VMware has to update the table of “where to find what block” (snapshot or base disk). This impacts performance significantly!


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