Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Usenet -> c.d.o.server -> Re: os io unit , db block size relation

Re: os io unit , db block size relation

From: FM <fabrizio.magni_at_mycontinent.com>
Date: Mon, 20 Sep 2004 09:12:26 +0200
Message-ID: <414E82DA.9010805@mycontinent.com>


Yong Huang wrote:

>
> Quite reasonable. Now the question is, if the filesystem was created
> with a block size different than memory page size (let's not talk
> about why), iostat wsec/s divided by wrqm/s should be roughly equal to
> page size or filesystem block size?
>
>

Sorry for the delay but I prefered to test before making any statement. The answer is: "file system block size".

Today, in the lab, I could set a test environment.

(Sorry is the below steps are abvious).

I created a file system with block size 1024.

mkfs.ext3 -b 1024 /dev/sda3

mounted it

mount /dev/sda3 /mnt/test

and issued:

iostat -d -t -x /dev/sda3 5

In another shell:

dd if=/tmp/foo of=/mnt/test/foo2 bs=1024k

and here the results:

Time: 08:47:05
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s avgrq-sz
avgqu-sz await svctm %util
/dev/sda3 0.00 0.00 2.00 0.00 4.00 0.00 2.00 0.00

    2.00
     0.10 50.00 50.00 1.00

Time: 08:47:10
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s avgrq-sz
avgqu-sz await svctm %util
/dev/sda3 0.00 10200.40 0.20 83.60 0.40 20568.00 0.20 10284.00 245.
45 67.92 810.50 31.03 26.00

Let's do the usually basic math:

wsec/s / wrqm/s = 20568.00 / 10200.40 = 2,017

Roughly two sectors of 512 bytes.
So my write were in blocks of 1k.
(Note: it has nothing to do with bs=1024k in the dd command).

This thread is becoming quiet useful even for me :) I'm having fun!

-- 
Fabrizio Magni

fabrizio.magni_at_mycontinent.com

replace mycontinent with europe
Received on Mon Sep 20 2004 - 02:12:26 CDT

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US