Steve,

Yep, this is possible. You can put a ZIL device straight into a head node, and create a pool with it. If you are in HA, you won't be able to handle a failover nicely though - I am not sure what the behaviour will be; either the pool will get imported and you lose ~10 seconds of writes, or alternatively the backup head won't be able to import the pool.

In the same situation, you can put L2ARC in the primary head node in HA. When you failover, your pool gets imported to the backup head, but it shows the pool as degraded because it can't see the L2ARC devices. This is fine though, no data loss, just some performance. (But the backup head would have to warm up the L2ARC in any case, so the performance loss is there anyway, just not permanent.) Hope that makes sense.

Yeah that makes sense, i also talked to nexenta support and they mentioned that there are other options for ZIL other than the STEC's, namely two OCZ Talos C drives mirrored (which halves that cost for me) so that is probably the way i'll end up going. I may consider L2arc in the head node tho.

Thanks for the info!

Not sure the advantage of mirroring the OCZ Talos if you're not going to mirror the STEC? In terms of data loss, you're only really guarding against against a failure of an OCZ and simultaneous loss of power or kernel crash etc. You don't get any more performance from ZIL by mirroring it.

The STEC will destroy the OCZ in performance after the initial 'freshness' you get with any flash SSD.

On the things we've got in production we use STECs mirrored, nothing else we've eval'd comes close.

Existing STEC we have will be for production once this unit is actually online (we're in no rush, plan to do lots of testing first) once in production we'll consider a second stec for mirror (for redundancy, understand you get no perf gain from it).

the reason i was looking @ cheaper ZIL options was because i want to be able to add a few other pools that are less production worthy without dropping the $$$ on the STECs

I'm aware that a STEC will blow away an OCZ talos, just want options thats all.

Thanks!

We chose to go with the Talos 2 R series instead of the C series, because the R series has capacitors inside to ensure that write cache is flushed in the event of a power loss. And I've read many different places that it is recommended to have ssd's with capacitors or whatever power-loss-protection. However I've also read that ZFS sends a flush-device-cache command on every synchronous write, so you would think that feature would negate the need for capacitors. I've also read that some ssd's ignore this flush-cache command to get better performance though, so I guess in any case it is most safe to get the ssd's with capacitors.