Let's say you have 200GB of database and 75GB of daily logs.  You will get better 
performance if you stripe both "disks" across five RAID groups than if you put the db 
on one and the logs on another.  

We have an HP XP-512, a storage frame comparable to (and IMHO better than) whatever 
model of Symmetrix was being sold in the last months of 2001.  Our initial disk layout 
for Exchange 2000 was very badly designed (gotta love VARs), with the db and logs 
sharing a single RAID group.  I recently took it upon myself to mitigate the design 
problem by moving the logs to another part of the frame but I did not detect any 
improvement in performance.  

Of course, it could be that we're just not hitting the server hard enough for disk I/O 
to be a problem.  In certain limited situations, yes it's better to separate the db 
LUNs from the log LUNs, but to optimize performance you need to consider what else is 
on these spindles, disk controllers, ports and port controllers (in XP terms, the 
parity groups, ACPs, ports and CHIPs), not to mention cache.  For example, if you have 
an I/O-intensive Oracle app on the same ports as Exchange, you may find that the port 
becomes a bottleneck regardless of where the Oracle data is stored.  These are the 
kinds of things your SAN administrators will consider when allocating disk space.  
Unless you have reason to doubt them, trust the SAN admins to know what they're doing.


-----Original Message-----
From: Anthony Sollars [mailto:[EMAIL PROTECTED]
Sent: Friday, April 16, 2004 2:00 PM
To: Exchange Discussions
Subject: Exchange 2k3 & SANs


Does anyone on the list have Exchange 2k3/2k running on an EMC SAN or other
comparable SAN product. We are getting a lot of push back from the SAN group
because we want to design our disk layout for optimum I/O performance and
have dedicated spindles for Exchange, and they don't feel it is necessary.
Do any of you have any real world experience with the pains of not designing
your SAN I/O properly and not following Vendor/MS best practices with disk
configuration? Thanks for the input, we are planning on engaging EMC and
performing some tests like these in there labs, but would like to get some
real world experiences from all of you.

Anthony Sollars
Sr. Technology Consultant
PACCAR Inc


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