Back in February, I uncovered an issue where backing up Virtual Machines on NFS storage, and using Change Block Tracking (CBT) was severely impacting VM performance. (<a href="http://blogs.egroup.jasonmangone.com/?p=3372"><strong>LINK</strong></a>). After digging into the issue, the best course of action was to turn off CBT.  CBT, when enabled, results in much faster backup times, but in this case the performance was not worth the performance hit.

I was on the phone recently with VEEAM's tech support, and we discussed VMware's recently released security patch, <strong><a href="http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&amp;cmd=displayKC&amp;externalId=1035108">ESXi410-201104401-SG</a></strong>, which specifically resolves the issue at hand. Below is a snippet from the release notes:
<p style="text-align: center"><a href="http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&amp;cmd=displayKC&amp;externalId=1035108"><img class="size-full wp-image-4205 aligncenter" src="http://blogs.eGroup-us.com/wp-content/uploads/2011/05/cbt.jpg" alt="" width="643" height="53" /></a></p>
 

I wanted to provide a follow up, and make sure everyone was updated. If you have been experiencing the issue and need to restore the tighter backup windows, then I recommend testing the patchby deploying to your test environment, turning CBT back for a couple test VMs, and checking full functionality by backing up. Once you have fully tested, proceed by rolling it into production.