[dm-devel] Re: DM performance issues

[Srini]

You can possibly run 'top' command parallely in another session to see
if the processor or memory is hitting the ceiling during this time.
That should give a clue hopefully.

Srini

On 3/8/07, Elliot Lee <sopwith at gmail.com> wrote:
> Sorry, I really should have given details on my system, especially
> the kernel version:
>
> Linux 2.6.19-1.2911.fc6 #1 SMP x86_64
>
> Pentium 4 3.00 GHz CPU, 1G RAM
> ext3 on LVM on RAID-5 on 5 * 500G SATA drives.
>
> Best,
> -- Elliot
>
> On Mar 7, 2007, at 19:36 , Elliot Lee wrote:
>
> > Hi all,
> >
> > I've got a 1.8TB LVM-on-RAID filesystem that was performing OK but
> > really didn't seem like it was going as fast as it should. I ran
> > the commands below and got some pretty startling results...
> >
> > A 60% performance hit for a linear mapping is heinous. What can I
> > do to help get this fixed?
> >
> > Best,
> > -- Elliot
> >
> > # dmsetup create foo --table '0 3880910848 linear 9:0 0'
> >
> > # dd if=/dev/md0 of=/dev/null bs=1048576 count=4096
> > 4096+0 records in
> > 4096+0 records out
> > 4294967296 bytes (4.3 GB) copied, 20.2362 seconds, 212 MB/s
> >
> > # dd if=/dev/mapper/foo of=/dev/null bs=1048576 count=4096
> > 4096+0 records in
> > 4096+0 records out
> > 4294967296 bytes (4.3 GB) copied, 55.3597 seconds, 77.6 MB/s
> >
>
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