[linux-lvm] Performance impact of LVM

[Sander Smeenk]

Hello list!

I've recently subscribed here as i have some questions about LVM,
particularly the performance impact of LVM on disk IO.

I'm a happy LVM user, on my workstation at home i've used it for a long
time. No special setups or anything, but it's nice to be able to resize
partitions on the fly, or have a number of disks act as one huge disk...

So, when I had to reinstall all servers for the company I work for, i
decided to use LVM for the same reasons stated above. But now i wonder:
Does LVM have any impact on disk IO? Are there any tests done on this
subject?

I couldn't really find any on the internet. Most of the things you find
are implementation issues and 'how does it work' stuff ;-)

I'm running LVM2 (2.02.06) on Debian 'sid' (unstable, but i hate that word)
using linux kernels 2.6.17.xx.

For example, one of my servers has 4x 34gb SCSI disks and 2x IDE disks.
One of the IDE disks has a 250MB boot partition, the rest is LVM
partition, the other IDE disk has one big LVM partition, same goes for
the 4 SCSI disks.

Then i made a scsi_vg01, with all the scsi disks and a ide_vg01 with all
the ide disks, and started lvcreating "partitions" inside those vg's.
That's basically how i set up LVM on all of my servers. Some servers
have different disk-configurations though...

Can anyone shed any light on this approach? Are there impacts on
performance of read / write actions? Any information is welcomed.

Hope to hear from you all!

Kind regards,
Sander.
-- 
| $ perl -e 'length q bless glob and print chr oct ord q mkdir m and print \
| chr ord q xor x and print chr ord q q q and print chr ord uc q map m and \
| print chr ord q qw q and print chr ord q each le and print chr ord q my \
| alarm and print chr oct oct ord uc qw q for q'  -  Don't you LOVE perl?