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RE: [dm-devel] 2.6 device mapper performance?



Hi Ming,

Thanks and I ran another block device read test by doing:
sync; time dd if=/dev/evms/.nodes/md/md3 of=/dev/null bs=1024k count=1024
AND
sync; time dd if=/dev/evms/volume1 of=/dev/null bs=1024k count=1024
the /dev/evms/volume1 is a evms volume on top of /dev/evms/.nodes/md/md3
And the results are (real/user/sys):
/dev/evms/.nodes/md/md3: 29.757s/0.020s/15.861s
/dev/evms/volume1: 41.697s/0.004s/25.586s

/dev/evms/volume1 took 12 seconds more to read the same amount of blocks.
Compare to 29.757 seconds it's about 40% more. Can we said it's introduced
by device mapper?

Ken

-----Original Message-----
From: Ming Zhang [mailto:mingz ele uri edu]
Sent: Friday, March 10, 2006 8:59 AM
To: ken hwang zyxel com; device-mapper development
Subject: Re: [dm-devel] 2.6 device mapper performance?


u have too many chances here. so hard to blame any one. suggest u to
test it one by one if possible.

for example, have same box run 2.4 and 2.6, test performance on volume
first before run xfs, and samba.

ming

On Wed, 2006-03-08 at 16:49 -0800, Ken Hwang wrote:
> Hi,
>
> I'm not sure I should ask this question here, if this is not the place
then
> I apologize. I have a home made NAS with Linux. I use evms to create
volume,
> put xfs on top of it, and then use samba to share it with Windows clients.
> When I was using kernel 2.4 with all the needed patches I could get
netbench
> 106Mbps with 4 clients, and 95Mbps with 8 clients. Recently I upgraded the
> same hardware to kernel 2.6 (I also upgraded the related application such
as
> samba, xfs utility, and dmsetup accordingly). Then I ran netbench again
and
> got 80Mbps with 4 clients, 53Mbps with 8 clients. Which drop almost 80%
(95
> vs 53) in 8 clients case.
>
> I then  make and mount xfs on another raid5 (which uses the same disk but
on
> different partitions) and found it got better performance (95Mbps with 4
> clients, 85Mbps with 8 clients). In brief:
> xfs volume on raid5 md/md1 on sda6/sdb6/sdc6/sdd6 netbench: 95/85Mbps
> xfs volume on EVMS volume /dev/evms/volume1 on raid5 md/md3 on
> sda8/sdb8/sdc8/sdd8: 80/53Mbps
>
> Do you think the slow down (85 to 53Mbps) was caused by device mapper?
> Please advice.
>
> Ken
>
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