ZFS on Hardware RAID controller

Eitan Adler eadler at freebsd.org
Wed Feb 19 01:28:35 UTC 2014

On Tue, Feb 18, 2014 at 5:27 PM,  <freebsd at fongaboo.com> wrote:
> When we spoke, you noted that when installing ZFS on multiple disks
> connected to a hardware RAID controller, it is best to config it to JBOD.

There are a few reasons for this.
(a) Hardware RAID serves as a single point of failure: if the
contoller dies you have neither disk
(b) As Andrew noted , using hardware RAID means that ZFS won't be able
to tell which disk is which.  The ZFS management tools won't work as
expected (they will show only one disk).
(c) Since ZFS implements RAID itself it can use knowledge about the
physical disks for better performance

Also see: https://en.wikipedia.org/wiki/ZFS#ZFS_and_hardware_RAID

> I tried to explain this to a colleague, but they were skeptical. Would you
> (or anyone) be willing to give me a one or two line sales-pitch on

"ZFS does RAID better than the controller."

>  why one
> should abandon traditional notions of RAID performance in favor of allowing
> ZFS to do disk management?

The goal isn't to give up on RAID but move its implementation to ZFS.

Eitan Adler
Source, Ports, Doc committer
Bugmeister, Ports Security teams

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