> I believe RAID-Z in a two-disk configuration is
> almost completely identical (in terms of space and failure resistant)
> to mirroring, but not an optimal implementation of it.
>
> If you want mirroring, you should just use mirror
> vdevs. Any ZFS folk want to chime in?
>
> Cheers,
> - jonathan
>
Shame on me....the man for zpool has most everything I needed (SX 4/06) except
confirmation from a 3rd party.
=========================================================
-bash-3.00$ uname -a
Sun Microsystems Inc. SunOS 5.11 snv_36 October 2007
-bash-3.00$ man zpool
Reformatting page. Please Wait... done
System Administration Commands zpool(1M)
NAME
zpool - configures ZFS storage pools
---snip---
raidz
A variation on RAID-5 that allows for better distribu-
tion of parity and eliminates the "RAID-5 write hole"
(in which data and parity become inconsistent after a
power loss). Data and parity is striped across all disks
within a raidz group.
[b]A raidz group with N disks of size X can hold approxi-
mately (N-1)*Xbytes[/b] and can withstand one device failing
before data integrity is compromised. The minimum number
of devices in a raidz group is 2. [b]The recommended number
is between 3 and 9.[/b]
=========================================================
The emphasis above is mine, but Jonathan appears correct in that there is no
compelling reason to even think about using RAID-Z for anything less than three
physical disks, no matter what way you slice up only two physical disks.
To summarize, if you only have two physical disks, forget about RAID-Z.
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