Erik Trimble writes:
> On Thu, 2006-09-28 at 10:51 -0700, Richard Elling - PAE wrote:
> > Keith Clay wrote:
> > > We are in the process of purchasing new san/s that our mail server runs
> > > on (JES3). We have moved our mailstores to zfs and continue to have
> > > checksum errors -- they are corrected but this improves on the ufs inode
> > > errors that require system shutdown and fsck.
> > >
> > > So, I am recommending that we buy small jbods, do raidz2 and let zfs
> > > handle the raiding of these boxes. As we need more storage, we can add
> > > boxes and place them in a pool. This would allow more controllers and
> > > move spindles which I would think would add reliability and
> > > performance. I am thinking SATA II drives.
> > >
> > > Any recommendations and/or advice is welcome.
> >
>
> Also, I can't remember how JES3 does its mailstore, but lots of little
> writes to a RAIDZ volume aren't good for performance, even through ZFS
> is better about waiting for sufficient write data to do a
> full-stripe-width write (vs. RAID-5).
>
> That is, using RAIDZ on SATA isn't a good performance idea for the small
> write usage pattern, so I'd be careful and get a demo unit first to
> check out the actual numbers.
>
IMO, RAIDZn should perform admirably on the write loads.
The random reads aspects is more limited. The simple rule of
thumb is to consider that a RAIDZ group will deliver random
read IOPS with the performance characteristic of single
device. That rule does not apply to either read or write
streaming data but only for small random reads pattern.
If that means you need to construct small RAIDZ groups
then do consider mirroring as an alternative.
-r
____________________________________________________________________________________
Performance, Availability & Architecture Engineering
Roch Bourbonnais Sun Microsystems, Icnc-Grenoble
Senior Performance Analyst 180, Avenue De L'Europe, 38330,
Montbonnot Saint Martin, France
http://icncweb.france/~rbourbon http://blogs.sun.com/roch
[EMAIL PROTECTED] (+33).4.76.18.83.20
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