On Tue, Jan 12, 2010 at 11:11:36AM -0600, Bob Friesenhahn wrote:
> On Tue, 12 Jan 2010, Gary Mills wrote:
> >
> >Is moving the databases (IMAP metadata) to a separate ZFS filesystem
> >likely to improve performance? I've heard that this is important, but
> >I'm not clear why this is.
>
> There is an obvious potential benefit in that you are then able to
> tune filesystem parameters to best fit the needs of the application
> which updates the data. For example, if the database uses a small
> block size, then you can set the filesystem blocksize to match. If
> the database uses memory mapped files, then using a filesystem
> blocksize which is closest to the MMU page size may improve
> performance.
I found a couple of references that suggest just putting the databases
on their own ZFS filesystem has a great benefit. One is an e-mail
message to a mailing list from Vincent Fox at UC Davis. They run a
similar system to ours at that site. He says:
Particularly the database is important to get it's own filesystem so
that it's queue/cache are separated.
The second one is from:
http://blogs.sun.com/roch/entry/the_dynamics_of_zfs
He says:
For file modification that come with some immediate data integrity
constraint (O_DSYNC, fsync etc.) ZFS manages a per-filesystem intent
log or ZIL.
This sounds like the ZIL queue mentioned above. Is I/O for each of
those handled separately?
--
-Gary Mills- -Unix Group- -Computer and Network Services-
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