> We're stirring up some strong opinions with my engineers on this
> end.
Um-hmm. :)
> Let me start by being clear. We're talking about HARDWARE RAID, not
> software.
Thought so.
> My understanding of when to use and not use RAID5 is that you want
> RAID1 for sequential file processing (like MS Exchange transaction
> logs) but RAID5 for all other processing, (like the OS and Exchange
> itself).
MS actually recommends RAID 0+1 for high-volume Exchange deployments.
> That would agree with Sandy's comment "RAID5 is for read-mostly
> applications". Doesn't that also complicate large corporation
> efforts to install SAN solutions for their corporate data including
> mail servers?
Yes, it does upend the idea of consolidating _all_ corporate data
within a disk subsystem with a single preferred access pattern
(read/write, write-mostly, read-mostly). Corporations must take stock
of individual server needs before deciding to throw everything out,
y'know?
> Or are there ways to make SAN solutions look like RAID1?
SANs will always look like plain old drives to the OS, just like
hardware RAID arrays; the underlying RAID can be 1, 5, whatever (SANs
aren't JBOD!).
> But what about Microsoft 2003 itself, and the Imail OS and IIS and
> the 3000 users that are going to access and manipulate their mail?
"Manipulation" of old mail on the web server, without deleting any
messages, will indeed by read-mostly (this would not be the case with
POP3 downloads, for comparison, as there each incoming message write
is accompanied by an outgoing message read). But you can't count on
this being the dominant usage pattern.
> Should the Imail directory (or even just the Domain and spool
> directories) be located on a RAID1 partition? And everything else on
> RAID5? Is that possible?
Sure, it's possible--IMail allows you to distribute several functions
across different paths, and you should dedicate as many spindles as
possible to each function for best performance--but I'd go with RAID
0+1 anyway, since it covers the most bases.
--Sandy
------------------------------------
Sanford Whiteman, Chief Technologist
Broadleaf Systems, a division of
Cypress Integrated Systems, Inc.
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