vStorage VMFS Version Notes

In a prior post, I mentioned that vStorage VMFS is one of my favorite elements of a VMware-based virtualization solution. With vSphere, the good news is that no action is required on the part of an administrator in the upgrade path. For fibre channel and iSCSI storage systems, here are some notes on VMFS versions that you can consider in your upgrade and deployment scenarios. And for the NFS camp out there, I'll get to you guys another day!

With ESX 4, the main thing you need to know is that versions of VMFS that started with ESX 3.x are forward compatible with ESX 4. If we look a little closer on this, some subtle details will start to emerge. Most VMFS volumes for ESX 3.x host systems were provisioned as VMFS version 3.21 volumes. When ESX 3.5 was introduced, we start to see VMFS version 3.31 assinged to newly created LUNs. Chances are if you have LUNs that have not been reformatted, you have a mixed environment in the versions of VMFS volumes.

When ESX 4 is introduced, we can still take advantage of the main benefit from the storage side: thin provisioning of the virtual disks, even for VMFS 3.21 volumes. For older versions of VMFS, we can miss out on some of the performance enhancements. Specifically, a VMFS 3.21 volume would not provide the same results as a VMFS 3.29 or higher volume. vSphere and ESX 4 will assign new LUNs at VMFS 3.33. For LUNs at VMFS 3.31, the difference between 3.31 and 3.33 is minor and marked as an internal change for VMFS.

The takeaway here is that if you can afford the time to evacuate each VMFS 3.21 volume that was initially provisioned in ESX 3.x and reformat it as 3.31 or 3.33, it may be a good idea. This can be made easy with Enhanced Storage VMotion, which allows a fully provisioned VM to be migrated to a thin provisioned disk. You have VMs to move anyways, so we might as well reformat the LUN upward if the opportunity is there.

VMFS is still the bombdizzle in the competitive landscape for virtualization filesystems from the hypervisor perspective. This is just a small note on versioning that can get everything in line as part of your upgrade planning process, either to vSphere or current versions of ESX 3.5.

Posted by Rick Vanover on 06/01/2009 at 12:47 PM