SAN based storage

[Michael Loftis]

--On April 19, 2006 12:47:26 PM -0500 John Wade <jwade at oakton.edu> wrote:

> We run cyrus on RedHat on a CX600.  For our administrative users, we put
> the whole thing on a nine disk fibre channel RAIDgroup, split into 6
> luns, 5 for mail spool partitions and 1 for all the other metadata.
> Total mail spool size is 300GB.   We average about 300 concurrent
> users.   The CX600 is heavily used by other applications.       I/O
> performance has never been an issue as far as I can tell.   The large
> write caches in the CX600 solve the write problem and the host memory
> caching seems to solve the read problem.    Your mileage may vary.     We
> couldn't do a direct cyrus  SAN performance comparision because when we
> moved to this box, we migrated to the SAN and new server hardware at the
> same time,  but tests on other systems where we just moved storage on to
> the array saw a huge performance boost vs. locally attached SCSI RAID 5
> storage with no write cache enabled.


Our mail cluster lives and dies by our CX200's write caches.  When they get 
turned off (as can happen during a failover rebuild on the SAN, or if you 
lose a vault drive) the mail cluster starts choking.  Even though we have 
used array's with write caching before the algorithms in the CX are 
definitely better.