When compared with our original configuration of Cascade arrays, our
addition of the EMC 3230 did, indeed, ameliorate many of our existing IO
problems.  Granted, no one technology is the absolute last word, but, at
this moment, I'm sold on EMC's ability to provide a more than adequate
alternative.  Other reasons for choosing EMC was the abililty to cram all
that DASD into our already burgeoning data center, plus the corporation's
experience with Symmetrix technology as part of their IBM mainframe
environment.  I think you're correct that the multiple-LUNs-per-spindle
configuration is probably a contributing factor to your IO performance hit,
and that's why I'll avoid the 9 - 23 GB HDAs like the plague -- at least
until the 3K supports fibre-channel connectivity.  Right now, we enjoy
average service times of 8-25ms from the EMC devices, and I'll do my best
to preserve that on future upgrades.  And, yeah, EMC is pricey -- that's
their biggest drawback, IMHO.

Thanks for your reply.
Lee Gunter     [log in to unmask]





From: [log in to unmask] on 04/29/98 08:25 AM


To:   Lee Gunter/BCBSO/TBG, [log in to unmask]
cc:
Subject:  RE: Arrays on MPEXL_SYSTEM. . .




In the past few months we have switched or production volume set from
JBOD to EMC Symmetrix 3700 with 16 x 23Gb spindles (each seen on the
3k as 6x4Gb) using 6 FWSCSI boards and 2Gb cache.  We installed the
first configuration as RAID S.  The (write) performance was so bad
that we had to reconfigure them RAID 1.  The performance is still not
great and we see service times comparable to yours, i.e., 60ms on some
of the EMC drives.  As you can see, the EMC will not resolve your IO
problems.  Application design appears to be the main problem here and
we are now addressing that issue (although I'm sure that the limited
number of spindles does not help).   Also watch out for the pricing.
 EMC has priced later add-ons. i.e., disk and cache much higher than
the original configuration.  We are now ordering 18Gb drives (will
configure them to be seen as 2 x 9Gb by the 3k) and adding another 2Gb
cache.  For the system volume set we use an HP Model 20 array (raid
1).  That appears to be working out fine.
-----Original Message-----
From:     Lee Gunter [mailto:[log in to unmask]]
Sent:     Tuesday, April 28, 1998 2:06 PM
To:  [log in to unmask]
Subject:  Re: Arrays on MPEXL_SYSTEM. . .
<snipped ... also snipped Denys' original post>