This post came about after a brief discussion with my pal, Lee Dilworth. Although the outcome of this test has really nothing to do with vSAN, the behaviour was observed on certain Guest OS which were running on vSAN. I guess the first thing that needs to be made clear is that there is no support for in-guest UNMAP (or TRIM) for VMs running on vSAN at this time, although it is something we are examining very closely. So with this in mind, we had feedback to say that a test being run as part of a proof-of-concept was showing…
A few weeks, my good pal Cody Hosterman over at Pure Storage was experimenting with VAAI and discovered that he could successfully UNMAP blocks (reclaim) directly from a Guest OS in vSphere 6.0. VAAI are the vSphere APIs for Array Integration. Cody wrote about his findings here. Effectively, if you have deleted files within a Guest OS, and your VM is thinly provisioned, you can tell the array through this VAAI primitive that you are no longer using these blocks. This allows the array to reclaim them for other uses. I know a lot of you have been waiting for…