Quick ZFS mirroring question for non-mirrored pool

[Jeremy Chadwick]

On Sun, May 16, 2010 at 04:29:23AM +0300, Kaya Saman wrote:
> On 05/16/2010 03:51 AM, Bob Friesenhahn wrote:
> >As long as the pool is not the boot pool, zfs makes such testing
> >quite easy.
> 
> I was under the impression that one needed a UFS2 filesystem in
> order to be able to boot FreeBSD as that is the only FS available
> upon install..... unlike Solaris10/OpenSolaris which creates the ZFS
> filesystem upon install.
> 
> The plan I originally conceived was to use a 40GB solid state disk
> as the / (root) directory comprising of all descending file systems,
> eg. /usr, /proc, /lib etc... using the UFS2 FS
> 
> ....and then use ZFS for the storage portion of my server using 2TB
> Western Digital RE4 Enterprise SATA drives.

I would highly recommend doing exactly what you've described here.  In
fact, it's what I do on two of my home systems (Intel X25-V 40GB drive
used for root, /usr, /var, and /tmp, and ZFS for everything else
including /home), and what I plan on our servers one Intel 80GB SSDs
drop to a more reasonable price.

There are many people here who have gone through the pain (IMHO) of
getting ZFS to boot on FreeBSD, and it still isn't as simple nor
reliable (in all configurations) as it is on OpenSolaris/Solaris 10.
There seem to be a large number of "gotchas" which come up when the
administrator least expects/wants it (usually during a failure
scenario).

Also, please reconsider going with Western Digital RE4 2TB drives.
These drives are all "GP" (Green Power) drives, which you do not want.
There have been numerous reports on the FreeBSD mailing lists about
problems with these drives (repeated head offloading/parking causing
problems in RAID arrays), and yes, it applies to Enterprise class drive
as well; WD has indirectly confirmed the problem in one user's case by
sending him a "fixed" firmware.  I can point you to threads if you want
to read them.

I would recommend you choose WD Caviar Black drives instead (cheaper,
benefit from TLER when enabled, and throughput is much higher than GP
drives), or another vendor of your choice.  Don't ask "Who do you
recommend?" because everyone has different experiences/preferences;
there's no vendor who's 99% reliable right now.  :-)

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |