VM snapshot needs consolidation

When a snapshot didn’t commit properly, it can happen that the snapshot manager in the vCenter server shows no snapshot(s), but that there are still active delta files on the datastore. These ‘hidden’ snapshot can cause the datastore to run out of space.

To report these ‘hidden’ snapshots (prior vSphere 5), I created a script that searches all the datastores  for ‘*.delta’ files and reported them by mail.

In vSphere 5 you have a new feature that reports and make it possible to consolidate these  ‘hidden’ snapshot(s). In vSphere 5 you get  a warning ‘Virtual machine disks consolidation is needed’ when the virtual machine snapshot consolidation has failed.


The snapshot manager shows no snapshots but there are delta files present on the datastore(s).

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In the vCenter server on the Virtual Machines tab you can enable the field “Needs Consolidation” to filter all the VMs that needs consolidation.


To consolidate the snapshot, right-click the virtual machine and choose Snapshot Consolidate.


Confirm the consolidate


Check the datastore and all the delta files are consolidated



With PowerCLI you can use the following one liner to list all the VMs that needs consolidation (thanks to Luc Dekens ):

Get-VM | where {$_.ExtensionData.Runtime.consolidationNeeded} | Select Name 


VMware ESXi 5 snapshot changes

In ESX(i) 3.x and 4.x snapshots files are default created in the virtual machine’s working directory (home directory). The working directory is the same directory as the were the virtual machine configuration (*.vmx) file is stored. 

snapshot-working basic esxi4


In this example a VM called “test” that has two disks (VMDK’s) placed on two datastores. The first disk is created on the VMFS01 datastore and the second disk is created on the VMFS02 datastore.  When a snapshot is created,  the VM “test”, the snapshot redolog (-delta.vmdk) files are place in the working directory (home directory). So the snapshots files are created on datastore VMFS01.


snapshot-working esxi4


In ESXi 5 the snapshot delta disks are stored in the same home folder as the base disk. On every disk a snapshot file is created.

snapshot-working esxi5


I have seen VMware ESX(i) 3.x and 4.x environments were only the working directory (home directory) is sized to store snapshot files . The other datastores didn’t have enough room for storing snapshot files.  So be sure before upgrading to vSphere 5 that all the datastores have enough free space to store snapshot files!

The snapshot location can changed in ESXi 5 but when performing a Storage vMotion, all the snapshot deltas will get migrated to the same folder as the VM’s base disk on the destination. 

Be sure to check this before upgrading to VMware vSphere 5!


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