Take Five With Tom Fenton

Working with VMware's Virtual SAN

Here are five tips that will help make your experience with VMware VSAN more productive.

• By Mike Matchett
• 08/12/2014

With more than 10,000 downloads, VMware Virtual SAN, or VSAN, is one of VMware's most successful beta programs. VSAN creates a pool of storage using the direct-attached storage of the physical servers in a VSAN cluster. While the software-defined storage approach is game-changing, what I find most interesting is that VSAN allows each VM to have its own storage attributes for things such as redundancy and performance. These attributes are then implemented and enforced by policy on a per-VM basis, independent of the underlying storage.

TAKE 1
Check the HCL. Check the HCL. Check the HCL. VSAN only supports a subset of the hardware that vSphere supports, so make sure the hardware you're going to use is on the VMware VSAN Hardware Compatibility List (HCL) at vmwa.re/vsanhcl. Hardware compatibility isn't strictly enforced by VSAN, but unpredictable results might occur if you use hardware not on the HCL. Trust me, I know.

TAKE 2
Get and use the latest software version. vSphere 5.5 U1 contains the VSAN bits and they're substantially different from the beta bits. Get the latest bits.

TAKE 3
Use the distributed vSwitch (DVS). VMware includes the right to use DVS with VSAN. The standard vSwitch will work, but VSAN uses the network extensively so use the DVS and give VSAN traffic high priority. VSAN can use 1Gb NICs, but if you have 10Gb NICs then use them, as a lot of VSAN traffic will go over the network.

TAKE 4
Make sure you have the hardware to test multiple storage profiles. VSAN requires a minimum of three nodes, and each node requires a minimum of a flash device (for caching) and an HDD (for persistent storage). However, to create interesting storage profiles, you'll want four or more nodes for failover testing, a few HDDs in each node for striping, and a large flash device for flash performance validation. Also, don't bottleneck your performance with inadequate network capacity.

TAKE 5
Monitor your VSAN cluster with VSAN Observer (vSOB). VSAN cannot be easily monitored using vSphere's traditional tools. You'll go crazy trying to use esxtop, which is the performance metrics tool in vCenter. Even vCenter Operations Manager is currently inadequate to monitor your VSAN deployment. vSOB is free, included in vSphere 5.5 U1, and it's a much better way to see how well the flash, disks, and hosts in a VSAN cluster are performing.

Bonus Tip
Use the Web! VSAN is new, but a few folks like Duncan Epping of Yellow-Bricks.com and Cormac Hogan at cormachogan.com (both work for VMware research and development) have done an excellent job of explaining how VSAN works and how you should work with it. Eric Sieber has an exhaustive list of VSAN links on his site.

Is VSAN "radically simple hypervisor-converged storage," and is it for you? Hopefully these tips can help you decide for yourself. Go forth and virtualize!