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Home -> Community -> Mailing Lists -> Oracle-L -> RE: I/O Performance/bottlenecks on EMC Symmetrix

RE: I/O Performance/bottlenecks on EMC Symmetrix

From: Greg Solomon <greg.solomon_at_betfair.com>
Date: Thu, 13 Sep 2001 08:38:25 -0700
Message-ID: <F001.0038D690.20010913083524@fatcity.com>

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Hi

Given that you don't seem to have access to the hardware, I'd suggest timestamping. Choose say a few dozen points in the process and collect timestamps at each one. Compare the prod timestamps to the test timestamps, something may jump out, eg one call taking 90 minutes instead of 30 seconds. I tend to put a lot of this sort of thing into my production systems anyway, it's the first place I look when a job slows down. Your duhvelopers may be able to help.

HTH
Greg

-----Original Message-----
Sent: Thursday, 13 September 2001 16:15
To: Multiple recipients of list ORACLE-L

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Hi,

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.

Jack

"Don Granaman" <granaman_at_home.com>@fatcity.com on 13-09-2001 16:15:25

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To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> cc: (bcc: Jack van Zanen/nlzanen1/External/MEY/NL)

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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!]

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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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Author: Don Granaman
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De informatie verzonden in dit e-mailbericht is vertrouwelijk en is uitsluitend bestemd voor de geadresseerde. Openbaarmaking, vermenigvuldiging, verspreiding en/of verstrekking van deze informatie aan derden is, behoudens voorafgaande schriftelijke toestemming van Ernst & Young, niet toegestaan. Ernst & Young staat niet in voor de juiste en volledige overbrenging van de inhoud van een verzonden e-mailbericht, noch voor tijdige ontvangst daarvan. Ernst & Young kan niet garanderen dat een verzonden e-mailbericht vrij is van virussen, noch dat e-mailberichten worden overgebracht zonder inbreuk of tussenkomst van onbevoegde derden. Indien bovenstaand e-mailbericht niet aan u is gericht, verzoeken wij u vriendelijk doch dringend het e-mailbericht te retourneren aan de verzender en het origineel en eventuele kopieŽn te verwijderen en te vernietigen. Ernst & Young hanteert bij de uitoefening van haar werkzaamheden algemene voorwaarden, waarin een beperking van aansprakelijkheid is opgenomen. De algemene voorwaarden worden u op verzoek kosteloos toegezonden.
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-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: INET: nlzanen1_at_EY.NL Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Greg Solomon INET: greg.solomon_at_betfair.com Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
Received on Thu Sep 13 2001 - 10:38:25 CDT

Original text of this message

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