freebsd-questions Digest, Vol 267, Issue 3

Adam Townsend desnudopenguino at
Tue Jul 14 04:58:00 UTC 2009

>>> A bit of reading shows that ZFS, if it's stable enough, has some
>>> really great features that would be nice on such a large pile o'
>>> drives.
>>> See
>>> I guess the last question I'll ask (as any more may uncover my
>>> ignorance) is if you need to use hardware RAID at all?  It seems
>>> both UFS2 and ZFS can do software RAID which seems to be quite
>>> reasonable with respect to performance and in many ways seems to be
>>> more robust since it is a bit more portable (no specialized
>>> hardware).
>> I've thought about this one a lot. In my case, the hard drives are in
>> a separate enclosure from the server and the two had to be connected
>> via SAS cables. The 9690SA-8E card was the best choice I could find
>> for accessing an external SAS enclosure with support for 8 drives.
>> I could configure it in JBOD mode and then use software to create a
>> RAID array. In fact, I will likely do this to compare performance of a
>> hardware vs. software RAID5 solution. The ZFS RAID-Z option does not
>> appeal to me, because the read performance does not benefit from
>> additional drives, and I don't think RAID6 is available in software.
>> For those reasons I'm leaning toward a hardware implementation.
> Hi Maxim,
> RAID-Z2 is the RAID6 double parity option in ZFS.
> gr
> Arno
I'm planning on doing something like this once I get 2 more 1TB
drives.  I'm going to try out a zfs RAID-Z not RAID-Z2, but yeah.
I've been around openSolaris' docs on zfs & it seems to be really
robust, you can export it on one OS and import it on another (incase
your root dies, or you want to migrate your disks to another box), you
can take "snapshots" which are stored on the drive, but I'm sure you
could send those files somewhere to be backed up.  And if you have
really important files you can create multiple copies of them
automatically with ZFS.  If you set it up with multiple vdevs, you can
get a lot more speed out of disk I/O as well, because if you have like
2 raidz vdevs, it stripes them, so you can pull data faster from both.
 I can't remember if it was on this or another list, but there was a
great discussion about the performance abilities/issues of zfs & they
had some good points like not using more than 8 drives per vdev &

Try it out both ways and see which is best.  there are pro's & con's
to both, but it all depends on what you need for your solution. &
remember raid is not a form of back-up.  so if this is for critical
information, make sure you back-up as well.


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