Wednesday, January 21, 2015

raidz

One of the more interesting things about ZFS is the raidz functions which are raidz, raidz2 and raidz3 - and are supposed to be technically equivalent or at least similar to RAID-5, RAID-6 and well there isn't anything comparable to raidz3 that I know of, anyway I recently had to setup a system using raidz, mostly because I don't trust the hardware RAID controller I am using anymore and just setup all the disks in what the card refers to as single disk mode, which is apparently different than JBOD at least the way this card does things.

I found this google doc that someone else made that explains all the cost involved in each raidz type as far as percentage of usable space afterwards.

If you want or need a crash course in raidz or zfs in general, this guide provides a lot of good documentation.

If you're just starting out with ZFS definitely look it over, especially the VDEVs section.

In case you're curious my new setup was 3 raidz vdevs of 5 1500GB disks in making one zpool which gave me 16T of space.

NAME        STATE     READ WRITE CKSUM
        vol         ONLINE       0     0     0
          raidz1-0  ONLINE       0     0     0
            da1     ONLINE       0     0     0
            da2     ONLINE       0     0     0
            da3     ONLINE       0     0     0
            da4     ONLINE       0     0     0
            da5     ONLINE       0     0     0
          raidz1-1  ONLINE       0     0     0
            da6     ONLINE       0     0     0
            da7     ONLINE       0     0     0
            da8     ONLINE       0     0     0
            da9     ONLINE       0     0     0
            da10    ONLINE       0     0     0
          raidz1-2  ONLINE       0     0     0
            da11    ONLINE       0     0     0
            da12    ONLINE       0     0     0
            da13    ONLINE       0     0     0
            da14    ONLINE       0     0     0
            da15    ONLINE       0     0     0

Also on the other side of this if you're using hardware raid it is probably always a good idea to use a third party utility such as Nagios, PRTG or whatever utility you may use to monitor it if possible. The good news for me is that the Nagios exchange shows several options for checking zfs and zpools so I'll be implementing that shortly. It seems that even PRTG can monitor ZFS via SNMP.