ZFS over RAID6

Matthew Seaman m.seaman at infracaninophile.co.uk
Wed Feb 9 17:14:48 UTC 2011

On 09/02/2011 15:21, $witch wrote:
> considerations :
> at lower level feel RAID6 meet my requirements (i love something that
> can face a double hw fault)

With ZFS that's called RAIDZ2 -- it's similar to RAID6 and it has the
same two-failure resilience characteristic.

> while at upper level ZFS looks very nice so am looking for such a
> combination.
> status :
> as now had found some ADPTEC, ARECA and 3WARE adapters that look
> reasonable but controller is not all;
> i need also 8 (+ 2 spare) HDs and a case where to keep them.
> so had extended research to 8HD cases with RAID6 capabilities.

Mixing ZFS and standard H/W Raid is not a good idea -- ZFS expects to
run on a collection of hard drives, not a composite disk array.  Instead
of paying for a RAID controller, put the money towards extra RAM and/or
SSD cards to use for the ARC and the ZIL used by ZFS.

If you want ZFS but you're stuck with built-in RAID, then it's best to
configure the RAID as a JBOD and use ZFS over that.

Hot spares and ZFS is a current development topic on FreeBSD: automatic
replacement of a failed drive doesn't work properly.  However, it should
be relatively easy for an admin to type commands to achieve the same effect.



Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
JID: matthew at infracaninophile.co.uk               Kent, CT11 9PW

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