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RE : RE : Poor ext3 performance on RAID arr ay



Title: RE : RE : Poor ext3 performance on RAID array

stride is the chunk size of your raid whatever the number of physical disks composing the RAID array.
So for 256k chunks with a block size of 4k, stride should be 256/4 = 64 instead of 640.

Maybe it will help.

Ionel


-------- Message d'origine--------
De: Rene Salmon [mailto:rsalmon74 gmail com]
Date: mer. 08/08/2007 22:53
À: GARDAIS Ionel
Cc: ext3-users redhat com
Objet : Re: RE : Poor ext3 performance on RAID array

Hi,

Thanks for the reply. I tried using the -E stride=X  option as follows:

mkfs.ext3 -b4096 -Tlargefile4 -E stride=640 /dev/dm-1

and got the same results around 50 MBytes/sec.  Maybe I have the wrong
number for stride so here is the math for that:

                          stride=stripe-size
                          Configure the filesystem  for  a  RAID  array
with
                          stripe-size filesystem blocks per stripe.


Here is some more detail on the RAID array.

RAID level : 5 (10 drives + 1 parity)
Chunk Size : 256 KB
Stripe Size : 2560 KB (10 drives * 256KB)

stride=640 * 4096(byte blocks) = 2560KB

I will try other stride options but they don't seem to change much.

Thanks
Rene




On 8/8/07, GARDAIS Ionel <Ionel Gardais tech-advantage com> wrote:
>
>  Hi Rene,
>
> You should try to add the "-E stride=X" option to the mkfs command line.
> Where X is expalined in the man page.
>
> This will basically map ext3 "blocks" on the RAID stripe size.
>
> Ionel
>
>
> -------- Message d'origine--------
> De: ext3-users-bounces redhat com de la part de Rene Salmon
> Date: mer. 08/08/2007 22:21
> À: ext3-users redhat com
> Objet : Poor ext3 performance on RAID array
>
> Hi list,
>
>
> I am having some strange performance issues with ext3 and I am hoping to
> get some advice/hints on how to make this better.  First some background
> on the setup.
>
> We have a RAID 5 array 10+1+1 with one LUN.  That is 10 SATA drives one
> parity drive and one dedicated spare.  The LUN is about 6.5TB.
>
> Using a 2Gbit/sec fiber channel card I can do some dd writes to the raw
> device and get speeds close to 200Mbytes/sec which is more or less the
> max the card can do.
>
> Next I create an xfs file system on the LUN and do a dd to xfs and get
> speeds close to 150Mbytes/sec.
>
> I want to use ext3 not xfs so next I put ext3 on the lun.  Now when I do
> the dd to the ext3 lun I get 25-50Mbytes/sec depending on whether I have
> the Raid controller cache turned on or off. Getting 50MBytes/sec with
> the raid controller cache turned off.
>
> I know that ext3 should perform better so I must be doing something
> wrong.  Here is my mkfs.ext3
>
> mkfs.ext3 -b4096 -Tlagefile4 /dev/dm-0
>
> Thanks in advanced for any help on this.
>
> Rene
>
>


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