Speedy storage server sales stumps sysadmin scribe: Who buys this?

Sysadmin blog Every once in a while I need to ask a question I know is going to get me in a world of trouble. It's the sort of question that triggers panicked emails from corporate PRs, and sometimes even the odd thinly veiled threat for daring to ask such things in a public forum.

I'm pretty lucky in that Chris Mellor, Storagebod, and others, usually ask these sorts of questions for me. I get the answer to the thing that's been bothering me for some time without the drama or bullies.

But every so often something bothers me enough that I feel compelled to start asking things I know are going to cause a fuss.

Finding a kernel of truth

The first question for which I have no answer involves VMware's marketing around VSAN. I'm baffled.

When VSAN launched we were flooded with marketing blurbage that claimed VSAN was better than competing server SANs because it was built right into the hypervisor. It's in the kernel! It's faster! Buy VSAN and not the other guys! It solves cancer and grows you a full, thick head of hair! Overwhelm social media and flood every single industry event with VSAN; go go go!

OK, OK, VMware; let me hit the pause button so I can compare a few things.

For at least the past 12 months (and probably longer) VMware has been saying they are ready for "100 per cent virtual". Any and every workload is ready to be virtualised. Their hypervisor is efficient, refined, and ready to take over the world.

I don't really question that assertion. In truth, I haven't been able to throw anything at VMware's hypervisor that it can't take like a champ … and I get paid good money to try.

But wait: a non-VSAN server SAN is just a virtualised workload. Maxta, Nutanix, SimpliVity, and so forth – these use VMs that "own" disks and SSDs on the local host using the hypervisor's raw disk mapping capabilities. Server SANs lash together multiple servers' worth of storage into one big pool of centralised storage that serves the whole cluster.

If VMware is ready to serve any workload – including the most ridiculously demanding tier-one enterprise applications, big data and so on – then shouldn't it be more than capable of running non-VMware server SANs?

In theory, being built into the hypervisor means that VSAN doesn't have to deal with the context-switching overhead that fully virtual server SANs experience.

In practice, this isn't supposed to matter: because VMware's hypervisor is made out of such amazing awesomesauce, time spent in the hypervisor is supposed to be completely negligible (especially given that you can allocate set amounts of RAM and CPU etc for a given VM, and do things like raw disk mapping; it makes the hypervisor's job a lot easier).

I personally see two conflicting assertions here: that VSAN is so much better than fully virtualised server SANs because it runs in the hypervisor, and that the VSAN-less hypervisor is so awesome it can easily handle any workload – like, er, fully virtualised server SANs.

No doubt someone will be along to tell me which marketing droids are correct and which are wrong.