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RE: I/O Performance/bottlenecks on EMC Symmetrix

From: Hallas John <John.Hallas_at_btcellnet.net>
Date: Thu, 13 Sep 2001 07:47:17 -0700
Message-ID: <F001.0038D1D5.20010913065020@fatcity.com>

Good list Don, and a dentist as well (repairing a bridge)!!!

-----Original Message-----
From: Don Granaman [mailto:granaman_at_home.com] Sent: 13 September 01 15:15
To: Multiple recipients of list ORACLE-L Subject: Re: I/O Performance/bottlenecks on EMC Symmetrix

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

WOW!† Is the "other" workload on these similar when this job runs?† Are you sure the problem is the Symmetrix and not something in the OS or instance configuration? Does this job spend a lot of time waiting (in Oracle) on physical I/O - or on something else?† (I guess if you don't have access to the machine, you can't find out though.† The ultimate tuning challenge!)

If the problem is actually Symmetrix I/O, I could only hazard a guess that it might be due to RAID-5 for something inappropriate (hot redo log files?) or extreme I/O contention in the layout.

As far as pointers, pitfalls, and suggestions...† I really have only one:† don't believe everything you hear!

For example: (top 10 list)
1) "With EMC, RAID-5 won't matter."† (it likely still will - for write-intensive stuff)
2) "With EMC, you don't want to stripe." (you might - it can still make a big difference)
3) "With the cache, I/O won't ever be a bottleneck."† (until cache becomes saturated or ...)
4) [Corollary to #3] "Throw out all that basic I/O tuning stuff you learned"
(but back it up to tape first!)

5) "The best layout is always SAME† - stripe and mirror everything across everything."
6) "The check is in the mail."
7) "This won't hurt a bit."
[ORA-00051] Drat!† I crashed before getting to ten!† Sorry, I was up all night repairing a bridge...

For more serious and less evasive answers, see Gaja's paper at http://www.quest.com/whitepapers/Raid1.pdf

-Don Granaman
[OraSaurus - Honk if you remember UFI!]

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

Hi All,

Does anybody here on the list have experience with EMC/symmetrix storage units.?

We have our databases on this machine and I have a feeling the the I/O performance is not very good. I can not proof it since I do not have any experience/data/access to that machine. We do however have a very cooperative UNIX group but they also lack experience with performance on this machine.

Who can give me pointers about I/O throughput that can be reached, configuration pittfalls etc..

Example:
RS6000 8CPU's and 4Gb memory with storage on EMC/symmetrix. Job takes about 2 hours to complete.

F50 1 CPU 1Gb memory (TEST machine) local disks. same job takes 0.5 hours to complete.

Jack



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† INET: nlzanen1_at_EY.NL


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Received on Thu Sep 13 2001 - 09:47:17 CDT

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