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RE: 10G and UFS - long write times

From: Stig Hornuff <>
Date: Thu, 08 Jun 2006 09:23:51 +0000
Message-ID: <BAY116-F164F2D769B2EABD7C6E975A18B0@phx.gbl>

As I read your description you are basically comparing I/O writes on SAN disks and local disks.
Is that what you are doing on various Oracle versions?

If it is, then note: Solaris using local disks (ie. in the very same box as the CPU) will Always perform a write all they way down on disk - verified writes!!
If disks are remote/attached Solaris "allows" itself to rely on writes being successfully submittet to the remote I/O-systems (ie. the SAN, T3, whatever....).

In simple words: Local disk are waaaaayyyyy slower than SAN and remote disk subsystems.


True Felix but that is not the point.

I wanted an easy script to recreate a problem

It does not explain why it takes say 30 seconds on 9i and 9 minutes on 10G on boxes that should be set up the same.

I use the word should carefully as I am assured we have a very conformant build standard that applies to all servers. I cannot guarantee that myself and frankly do not have the skills nor the time to do so.


From: [] Sent: 08 June 2006 09:19
To: Hallas, John, Tech Dev; Subject: AW: 10G and UFS - long write times


if you're really using this script you're issuing 50000 commits - no wonder it takes so long. Make the commit at least outside the loop!


-----Ursprüngliche Nachricht-----
Von: [] Im Auftrag von Hallas, John, Tech Dev
Gesendet: Donnerstag, 8. Juni 2006 10:16 An:
Betreff: 10G and UFS - long write times

We are seeing big problems when issuing disk writes using 10G (both 10.1 and 10.2). Reads are not an issue

Very difficult to track down the exact combination but so far it looks as if it is a combination of 10G and local disk mounted using UFS .

V440 Solaris servers could also come into the combination because that is what I have done a lot of the testing on as that is what is available. I have now tested on around 10-12 servers with consistent findings.

The test is very simple and quick to do. Searching Metalink and WebIV does not give any clues. I am about to log a tar but I know I will require all sorts of Unix information which is quite long-winded for me to get so any help would be appreciated.

The test

CREATE TABLE test( a number, b CHAR(2000) )tablespace xxxx ;

Set timing on

BEGIN        FOR r IN 1..50000 LOOP

             INSERT INTO test (a,b) VALUES (r, 'test');

             COMMIT;        END LOOP; END On SAN disk and 9i on local UFS mounted disk I am seeing response times from 0:15 to 0:30 seconds

On 10G on San I see the same

On 10G using local UFS disk the time various from 7:00 to 9:00 minutes and is very repeatable.

I have tried around 10 servers now and the results are consistent.

Whilst we have quite a few 10G installations, not many are on local disk and the majority are on Sun 440 (2.9 OS) so my results may indicate a UFS problem when it could be an OS one (or an Oracle one of course). OS writes to disk are stable at twice as fast on San as local disk and the fact that 90i does not show a problem seems to take away the OS part out of the equation. But nothing is certain yet.

PS the waits are all IO related - log buffer , log file sync etc

Thanks for any help


Received on Thu Jun 08 2006 - 04:23:51 CDT

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