RE: 2.6 device mapper performance?

[Ming Zhang <mingz@ele.uri.edu>]

if possible, (if u have no data on it.) can u do dd write?

u now build evms over raid?

can u do blockdev -getra /dev/evms/volume1?

ming


On Fri, 2006-03-10 at 12:01 -0800, Ken Hwang wrote:
> 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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