Re: I/O and db_file_multiblock_read_count
- From: "Jared Still" <jkstill@xxxxxxxxx>
- To: kmoore@xxxxxxxxxxxx
- Date: Mon, 11 Dec 2006 12:46:06 -0800
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@xxxxxxxxxxxx> 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@xxxxxxxxxxxxx
> [mailto:oracle-l-bounce@xxxxxxxxxxxxx] 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
>
>
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--
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist
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