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Re: RE : Poor ext3 performance on RAID array


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:

                          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.


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.


-------- 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.


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