I posted a week or so ago about the ESXCLI UNMAP process with vSphere 5.5 on the Pure Storage FlashArray here and came up with the conclusion that larger block counts are highly beneficial to the UNMAP process. So the recommendation was simply use a larger block count than the default to speed up the UNMAP operation, something sufficiently higher than the default of 200 MB. I received a few questions about a more specific recommendation (and had some myself) so I decided to dive into this a little deeper to see if I could provide some guidance that was a little more concrete. In the end a large block count is perfectly fine–if you want to know more details–read on!
One of the main things I have been doing in my first few weeks at Pure Storage (which has been nothing but awesome so far by the way) is going through all of our VMware best practices and integration points. Testing them, seeing how they work or can they be improved etc. The latest thing I looked into was Dead Space Reclamation (which from here on out I will just refer to as UNMAP) with the Pure Storage FlashArray and specifically ESXi 5.5. This is a pretty straight forward process but I did find something interesting that is worth noting.
One of the documents that my colleague Drew Tonnesen (@drewtonnesen) and I maintain is a white paper that explains the how, what, why, when, etc. of using VMware’s VAAI block primitives (WRITE SAME, XCOPY, ATS and UNMAP) with Symmetrix VMAX storage systems. We update this document around twice a year or as needed to take into account new Enginuity releases or VMware releases. We just posted the latest update this weekend on EMC’s website: