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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