Exchange Server - recommended disk configuration?

Asked By Kremlar

19-Nov-09 10:43 AM

We're currently putting together a new server to host Exchange for
organization, about 50 users.

We're using a chassis that supports up to 6 drives, using a decent SAS/SATA
RAID card with battery backup.

Our budget will not allow for 15K RPM SAS drives, so we are looking at 10K SATA
drives.  Wondering how best to use our 6 available drive bays to get optimal
Exchange performance.

Should we go with:

2 drives in a RAID1 configuration
+3 drives in a RAID5 configuration
+hotspare

or

5 drives in a RAID6 configuration
+hotspare

My understanding is that Exchange performs better with 2 physical arrays
versus a single array with multiple partitions.

Any advice?

19-Nov-09 04:17 PM

Let's assume you are asking about Exchange 2007 since you did not say.
However, my answer pretty much applies to any version.

If you are limited to six drives, I would go with:
2 drives in RAID-1, partititioned into two, one for OS + Swap File and the
other for Exchange logs
4 drives in RAID-1 or RAID-5 for the databases
and skip the hot spare, maybe buying an additional cold spare if your
service contract does not provide for fast replacement.

The reason behind two arrays is not so much performance as recoverability,
especially with just 50 users.  You want to keep the logs and databases on
separate physical volumes so that if you lose either one, after recovering
you can still get all your data back up to the point of failure.
--
Ed Crowley MVP
.

19-Nov-09 04:43 PM

Hi Ed -

Thanks for your reply.  Yes, 2007.  Since performance is not so much an issue
with 50 users, any reason why you would  recommend against a 3-drive RAID5
leaving the 6th drive as a hotspare?

Replacement of a dead drive would be fairly quick, but my nightmare scenario
is a disk failure on a Friday evening that is not attended to until the
following Monday.  A hotspare would make me feel better.

20-Nov-09 02:24 AM

With so few drives the hot spare would be a waste, in my opinion.  You
already have hot spares in both RAID configurations.  Instead put the drive
in service and give people bigger mailbox quotas.  Get a monitoring system
that pages you when your disks die.
--
Ed Crowley MVP
.

23-Nov-09 06:40 AM

I would not and we do not bother with 'hot' spares, they are
spindles are running and burning their life away just as
much as the drives they are supposed to be backing up.

Have a spare or two sitting on a shelf ready to be pressed
into service, your raid is fault tolerant anyway - that is
you can drop a single drive without losing the system, just
replace the dead drive when it fails and if remainder drives
are near to the MTBF replace them all one by one rebuilding
the raid as you go.

and as other have suggested, make sure or get the raid
monitoring software for your system,

- and implement a backup system for your data - do not rely
on the raid - you never know.....

good luck...