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Re: I/O and db_file_multiblock_read_count

From: Jared Still <jkstill_at_gmail.com>
Date: Mon, 11 Dec 2006 12:46:06 -0800
Message-ID: <bf46380612111246pc8ab2f7x4478e0623597e46b@mail.gmail.com>


Adding fuel to the fire.

This on a somewhat busy Dual CPU linux box. The SAN is Clariion CX700.

Disk is a dedicated RAID10, though I'm not positive about the number of spindles. There are I believe 6 spindles.

The command was run once, then both run to account for SAN caching.

time dd if=/u01/oradata/dv04/cimindxsmall_01.dbf of=/dev/null bs=1048576 1500+1 records in
1500+1 records out

real    0m1.207s
user    0m0.002s
sys     0m1.205s

time dd if=/u01/oradata/dv04/cimindxsmall_01.dbf of=/dev/null bs=65536 24000+1 records in
24000+1 records out

real    0m0.744s
user    0m0.014s
sys     0m0.729s

Interesting that the 64K blocksize significantly outperforms the 1M blocksize.

On 12/11/06, Keith Moore <kmoore_at_zephyrus.com> wrote:
>
> We also use Hitachi Sans. I ran dd for 64K and 1M block sizes and the
> reads
> with 1M block size were slightly faster. This is on Solaris8 / Sunfire
> 15K.
>
> Strangely, the sys time is much lower with the 1M blocksize. Is there an
> explanation for that?
>
> Keith
>
> orapls> time dd if=polaris_data_04.dbf of=/dev/null bs=65536
> 163840+1 records in
> 163840+1 records out
>
> real 4m15.57s
> user 0m0.85s
> sys 2m37.34s
> ddcspora07 - pol2p - /plsoraprd01/u03/oradata/pol2p
>
> orapls> time dd if=polaris_data_04.dbf of=/dev/null bs=1048576
> 10240+1 records in
> 10240+1 records out
>
> real 3m59.18s
> user 0m0.02s
> sys 0m21.93s
>
>
> > do the "same" thing using dd. Whatever your db_block_size is, plug it in
> > as follows:
> >
> > $ time dd if=<datafile_for_the tablespace> of=-/dev/null
> > bs=<block_size_in_bytes*16>
> >
> > then re-run:
> > $ time dd if=<datafile_for_the tablespace> of=-/dev/null
> > bs=<block_size_in_bytes*128>
> >
> > please let me know what you find
> >
> >
> >
> >
> > ________________________________
> >
> > From: oracle-l-bounce_at_freelists.org
> > [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Kevin Lidh
> > Sent: Friday, December 08, 2006 12:46 PM
> > To: oracle-l
> > Subject: I/O and db_file_multiblock_read_count
> >
> >
> > I was reading an article about the appropriate setting for
> > db_file_multiblock_read_count. I'm on a HP-UX 11.11 64-bit system with
> > Oracle 9.2.0.7.0. The original value was 16 and I bounced the database
> > and ran a million record full-scan test (10046 trace) and then set the
> > value to 128 (max value) and re-ran the
> >
> >
>
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

-- 
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist

--
http://www.freelists.org/webpage/oracle-l
Received on Mon Dec 11 2006 - 14:46:06 CST

Original text of this message

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