[linux-lvm] performance probs: snapshots on mp-systems

[Heinz J . Mauelshagen]

On Mon, Dec 17, 2001 at 05:51:52PM +0100, Martin Petermann wrote:
> Hi all,
> 
> I have running SuSE 7.2 (2.4.4 kernel) on a dual processor machine (2x833
> Mhz Pentium III). I made a snapshot of the following configuration:
> 
> >lvcreate -L 100M -n snapshot -c 4 -s /dev/vgfortest/testfs1
> lvcreate -- WARNING: the snapshot will be automatically disabled once it
> gets full
> lvcreate -- doing automatic backup of "vgfortest"
> lvcreate -- logical volume "/dev/vgfortest/snapshot" successfully created
> 
> peanuts:root /
> >lvscan
> lvscan -- ACTIVE            "/dev/mediastore/data" [100 GB]
> lvscan -- ACTIVE            "/dev/vgfortest/bigfs" [8 GB]
> lvscan -- ACTIVE   Original "/dev/vgfortest/testfs1" [500 MB]
> lvscan -- ACTIVE            "/dev/vgfortest/testfs3" [500 MB]
> lvscan -- ACTIVE            "/dev/vgfortest/smallfs" [60 MB]
> lvscan -- ACTIVE   Snapshot "/dev/vgfortest/snapshot" [98.54 MB] of
> /dev/vgfortest/testfs1
> lvscan -- ACTIVE            "/dev/zweite_testvg/testfs1" [500 MB]
> lvscan -- ACTIVE            "/dev/zweite_testvg/testfs3" [500 MB]
> lvscan -- ACTIVE            "/dev/zweite_testvg/testfs" [200 MB]
> lvscan -- 9 logical volumes with 110.3 GB total in 3 volume groups
> lvscan -- 9 active logical volumes
> 
> The vg vgfortest is on a fc disk.
> 
> This first run I did in multi processor mode:
> 
> >time cat /dev/vgfortest/snapshot > /BIGFS/file
>  1136.72s real     0.13s user    15.87s system
> 
> in single processor mode:
> 
> peanuts[root]/> time cat /dev/vgfortest/snapshot > /BIGFS/file
>   402.03s real     0.10s user    16.16s system
> 
> Is this problem known? Does there exist a fix?

Martin,

have heard about it for the first time.
Have you tried a newer kernel with the recent VM enhancements?

> 
> Thanks for any help!
> 
> Martin
> 
> 
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-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen at Sistina.com                           +49 2626 141200
                                                       FAX 924446
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