VMware ESXi Snapshot Placement

Recently I came across an issue after recently upgrading an environment from ESXi 4.1 to ESXi 5.1 update 1 when I started to get issues with snapshots filling up LUNS.  After analysing what was going on I noticed that when a snapshot was initialized, the snapshot file placement was different and was causing space issues.

On ESX 4.x environment the delta disks were stored in the directory specified by the workingDir parameter. This was typically the same directory as the configuration files for the virtual machine

On ESXi 5.x environment to facilitate the improvements to Storage vMotion and the new Storage DRS feature, a change to the snapshot process was introduced with ESXi 5.0. The workingDir parameter still exists but it now only affects the placement of the snapshot .vmsn file. So therefore delta disks are stored on each and every base disk associated with the virtual server

To revert to the pre-ESXi 5.0 way of storing snapshots in the directory specified by the workingDir parameter, the new snapshot.redoNotWithParent parameter must be added to the virtual machine’s configuration(.vmx) file.

Note: This procedure is used in conjunction with the workingDir parameter

To configure the snapshot delta files to be kept in the same directory as the location specified in the workingDir parameter, you must add the new parameter snapshot.redoNotWithParent to the virtual machine configuration file(.vmx).

To set the snapshot.redoNotWithParent parameter:

1. Power off the virtual machine and commit any existing snapshots
2. Right-click the virtual machine and click Edit Settings.
3. Click the Options tab.
4. In the Advanced Options, click General.
5. Click Configuration Parameters.
6. Click Add Row.
7. In the Name field, type snapshot.redoNotWithParent.
8. In the Value field, type true.
9. Click OK to save the configuration parameters.
10. Click OK to save the virtual machine settings.
11. Power on the virtual machine.

Note: This can also be achieved by editing the .vmx configuration file of the Virtual Machine.

So make sure that you have enough space on each LUN if you don’t want to revert back  to the pre ESXi 5.x way of snapshots.