Re: 10g System statistics - single and multi

From: Paul Drake <bdbafh_at_gmail.com>
Date: Wed, 18 May 2005 14:47:53 -0400
Message-ID: <910046b40505181147515a6ea5@mail.gmail.com>

On 5/18/05, Christo Kutrovsky <kutrovsky.oracle_at_gmail.com> wrote:
> Wolfgang,

>=20

> I will have to repeat this test on my system. What was your OS and
> file system ? linux and ext3 does not have directio support. It also
> has poor default read-ahead parameters.

>=20

> "...on average it should take the same amount of time to position ..."
> If you were to do 1 x dfmrc randomly, then yes mread would always be >
> sread. But you are doing this sequencially. Thus only the 1st read
> would involve positioning the heads, after that, every subsequent read
> would not include that time. Every so often, there would be some time
> to move the head to next track, but this time is far less then a full
> seek time. That is, of course, assuming no other disk activity. Or
> minor activity.

>=20
> Unfortunelly the test 10g system I have is not yet on the SAN i am testin=
g.

>=20

> I am using RedHat linux and ASM (i.e. using directio)

>=20

> These results have been produced with Windows (for convenience) on
> unpartitioned drives with iometer (www.iometer.org). No caching on OS
> side.

>=20


> Random read from my SAN

> Test type       Responce time (ms)

> 512 read-1=3D090.874

> 512 read-2=3D090.173
> 512 read-4=3D090.130
> 8k read-1=3D090.457
> 8k read-2=3D090.149
> 8k read-4=3D090.228
> 32k read-1=3D090.422
> 32k read-2=3D090.388
> 32k read-4=3D090.762
> 256k read-1=3D092.165
> 256k read-2=3D092.672
> 256k read-4=3D095.185

>=20

90 milliseconds for a single IO? what are you using, a 5 year old laptop? Can you run a sanity check against sys.V_$FILESTAT to make sure that you're on the right order of magnitude?

This sounds like you need to watch the movie "Office Space" repeatedly. Pay particular attention to the part where Micheal Bolton is chastised for not keeping proper track of the decimal (US-centric) point. They end up headed for trouble, but predictably so as the movie came out of hollywood, they avoid _hard_ time in a federal (pound me ...) prison.

You cannot be averaging 90 milliseconds for an IO on a healthy system. I don't think that I could get that if I set every parameter backwards, disabled all of the indexes and set the pga_aggregate_target to 4M. Guess it might be worth a try. I guess that its possible if you are running RAID 5. baarf.

Paul

--=20
#/etc/init.d/init.cssd stop
# f=3Dma, divide by 1, convert to moles.

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Received on Wed May 18 2005 - 14:52:33 CDT