virtualization - virtual san appliance in esxi? why?

I am looking at different SAN solutions (Starwind, Lefthand, OpenFiler, OpenSolaris, etc.) for my small office and I understand that there are many virtual SAN appliance (VSA) solutions which can be used with ESXi.

Does anyone use it in a mission critical environment?

Let's see if I got it right:

In order for the SAN VM to "see" the harddisks, ESXi would have to "see" it first right? I'm assuming you would have to install the SAN VM on a local datastore, AND allocate space on a local datastore for the SAN VM, something like this:

• USB boot ESXi


• RAID card with local disk array A (For OS)


• RAID card with local disk array B (For SAN)


• Install SAN VM on local disk array A


• Use local disk array B as SAN datastore



• Share SAN datasore with other ESXi machines

Are there advantages to this kind of setup? It seems a little overcomplicated to set it up this way, isn't it? How does this support HA?

Answer

Does anyone use it in a mission critical environment?

I'm sure some do yes.

In order for the SAN VM to "see" the harddisks, ESXi would have to
"see" it first right?

Correct.

You're generally right about the start-up sequence although in most cases it'd actually be more like;

• Boot ESXi from local hard disk/array


• Auto-start Storage VM from local disk datastore


• Storage VM then shares out local disk datastore using iSCSI/NFS etc. to any ESXi host.


• Any of the ESXi hosts can then start any VMs contained in shared storage.

The advantages of this approach is that it's very cheap, local DAS is always going tobe cheaper than centralised resilient SAN arrays. Some storage VMs also cluster to offer a sort of 'RAID of VMs' to increase resilience.

Personally for MC work I would use centralised SAN arrays but I have the budget, others don't and some of these storage VM systems can be configured to be surprisingly fast and resilient.