Is this pool setup a bad idea?

[Fahad Chaudhri]

Hello,

We have a Freenas server that provides iSCSI to a Vmware cluster. The Freenas box has a pool with 3 drive RaidZ1 vdevs and a spare drive. Is this pool setup a bad idea? Is there any befit of setting up the pool this way? Would a pool with 2 drive mirrored vdevs be a better option?

Thanks.

 

[sretalla]

For iSCSI, you probably want max IO performance, so this is not optimal in that sense. (mirrored VDEVs is what you want for that)

You are maximising your storage capacity (to an extent) with your current setup, but at the risk of data loss and reduced IO performance.

The drives are small enough that you would not see others from the forum berating you for not going with RAIDZ2 and it would only put you in the same pool risk as mirrors anyway.

I guess you have done the reading in the resources section on ZFS to understand that if you lose 2 disks in the same VDEV, your whole pool is gone/requiring restore from backup. (as I mentioned, the same in the case of Mirrored VDEVs)

Hot spares are rarely of actual utility as the disk needs to be seen as completely dead before the auto replacement will happen. They only really serve to help in the case where you can't physically get to the location of your server in a reasonable amount of time.

If you have VDEVs of unequal size, you will not get a good balaning of the IO in the pool across all VDEVs.