[linux-lvm] LVM performance

[Duncan Young]

I hope this isn't stating the obvious, but I asume you have used hdparm to 
adjust the default setting on your drives appropriatly (i.e. dma).  I have 4 
disks striped and get average sequential throuput of at least 40mb/s and 
35mb/s (dd to /dev/null) on only 2 disks.

cpu is approx 60% system (666mhz system).

If I have the disks untuned I get %100 cpu, machine "stuttering" and throuput 
10 times less.

Duncan

On Friday 23 Nov 2001 4:17 am, you wrote:
> Hi all,
>
> All right. I've got LVM installed and running on 2 30GB IDE drives, a VG on
> each, and the partitions divided just about evenly between them. This is on
> a 1GHz Athlon with 640MB of RAM. I am running Debian/sid with lvm 1.0.1rc4
> and kernel 2.4.13.
>
> A few things I have noticed in the week or so that I have been using LVM.
> First, the drive activity light stays lit all the time. I'm not terribly
> worried about it, since things seem to be behaving normally, but I figured
> I would ask.
>
> The second, and far more disturbing thing is that any heavy accesses to the
> filesystem (copying large files, scp-ing files mastering CDs, anything with
> a lot of IO brings my machine to its knees. Case in point. When I started
> this message, I was mastering a CD using xcdroast, which had called
> mkisofs. Not only did the mastering take (I'm guessing here, since I didn't
> note the time) about 10 minutes, the load average jumped, at one point, to
> 8.23, and generally hovered around the 6-to-7 range. Copying large files
> from filesystem to filesystem on the machine yields similar results.
> Originally, I had the following configuration:
>
> hda 30GB HD
> hdb 30GB HD
> hdc DVD-ROM
> hdd CD-RW
>
> A friend suggested moving the HD on hdb to the other channel, so now the
> drives are on hda and hdc, the dvd is on hdb and the cdrw is on hdd.
>
> Can anyone give me any ideas as to why the machine gets beaten about so
> much during IO operations and more importantly how can I minimize the
> impact.
>
> Regards,