# ZFS on iSCSI on ZFS



## kgatan (Oct 29, 2012)

If I have a number of machines with ZFS raid (doesn't matter which level) in a data centre, would it be possible to share these machines with iSCSI as single LUN's and stripe or raid them on a kind of ZFS master server?

It would give protection against disk failure on the iSCSI machines, and also protection against machine failure if you raid the ZFS master server with the underlying LUN's.

Perhaps its better to share all disk as separate LUN's and then use nested raid on the ZFS master server to protect against both machine and disk failure?

I have no experience what so ever with this so in case this is an insane question then I'm sorry


----------



## olav (Oct 30, 2012)

Yes you can use two SAN's and setup a mirrored ZFS storage by accessing two LUN's. However there are a few things that you have to keep in mind.
FreeBSD's iSCSI initiator isn't working too well. Especially if a LUN goes offline, it can hang/freeze your whole system.
You should keep the LUN volumes small and always keep an eye on performance. Resilvering/scrubbing takes time.
HAST will most likely be a lot better than creating a ZFS mirror of two LUN's.


----------



## kgatan (Oct 30, 2012)

Ah, yes didn't think of that.
Is resilver and scrubbing time dependent on iops or raw throughput?


----------



## Crest (Oct 31, 2012)

Depends. It reads the live blocks in chronological order. Given the average size of blocks for most setups it's limited by raw throughput.


----------

