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Re: I/O Performance/bottlenecks on EMC Symmetrix

From: Jonathan Lewis <>
Date: Thu, 13 Sep 2001 12:16:40 -0700
Message-ID: <>

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I have had, and heard of, poor performance from EMC boxes before now because of the big black box principal.

You might check out James Morle's book
(scaling Oracle 8i) for some thoughts.

>From an Oracle perspective, you may

find that simply checking v$filestat
will demonstrate quite clearly that
the average read time off disk is very
poor - the last big site I went to were
getting read times of worse than
100 millisecs - when EMC were claiming
to offer better than 20 millisecs.

If this doesn't help, there is a C program on my web-site (under a Miscellanous
or Performance article on choosing a
block size) which allows you to create
a file, and then start emulating random
"Oracle-read" I/Os - this should give
you a quick way of testing the real
response time of the black box.

Jonathan Lewis

Host to The Co-Operative Oracle Users' FAQ

Author of:
Practical Oracle 8i: Building Efficient Databases

Screen saver or Life saver: Use spare CPU to assist in cancer research.

-----Original Message-----
To: Multiple recipients of list ORACLE-L <> Date: 13 September 2001 16:30

!! Please do not post Off Topic to this List !!


The other workload I would say was about the same (Relatively speaking)
Both machines did have idle time on the CPU (I/O intensive job). The quicker test machine was a bit stretched on memory at the time (running
about 8 databases) but not too bad.

The only thing I can think of is pi** poor performance (3 p's you don't
want in marketing) of the symmetrix disks.

One point this symmetrix is loaded with 36 Gb disks and all of them are
sliced to pieces and than allocated to filesystems. In theory you can be
sharing disks with other high I/O apps (E-mail system etc..). I do not however have any insight in what is where physically.


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Author: Jonathan Lewis

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Received on Thu Sep 13 2001 - 14:16:40 CDT

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