I posted the following fragment in answer to a similar question back in
early April:
"If the controller will be connected to an FC card on the 3000, you
should create a maximum of 16 LUNs (ldevs) (20GB each). If the array
will be connected via an HVD or LVD SCSI connection, plan on a maximum
of 8 LUNs (ldevs) (40GB each). If it's connected via SE-SCSI, plan on
updating your resume. Just kidding, don't do it that way."
Obviously, you need to recalculate the LUN sizes given your array size.
Denys
-----Original Message-----
From: HP-3000 Systems Discussion [mailto:[log in to unmask]] On
Behalf Of John MacLerran
Sent: Thursday, May 13, 2004 12:34 PM
To: [log in to unmask]
Subject: [HP3000-L] VA7100 Questions
Dear HP-3000-L,
We just received a refurb VA7100 Array to replace two Nike Mod 20s on
our
N4000 MPE box (woo hoo!). We purchased it with ten 36-gb discs, and I
have a
couple of questions about how best to partition the lil' beastie for
performance.
I've read that MPE gets the best performance wrt disc i/o by having
"lots of
small luns" -- my questions are: How many is "lots"? and How small is
"small"?
By trial and error, I've discovered that the current raw configuration
of
the array yields about 165GB (in RAID 1/0, which is how we'll use it,
because we don't want the RAID5 write performance hit). I could
partition
that into fifteen 11gb luns, or eleven 15gb luns, or twenty 8gb luns and
a
5gb lun. If I want to go really crazy, I could do fifty-five 3gb luns,
but
that seems overkill. Is there a point of diminishing returns?
Also, given that MPE 7.5 can use space beyond 4gb on LDEV1, is there an
advantage to keeping that lun smaller than the others (the 5gb lun in
the
20/8 scenario above)? Assuming, of course, that I can tell the array
which
lun I want to correspond to LDEV1 when I run mapper and fcscan after we
get
the adapter cards installed.
Any insight?
Thanks!
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