Re: mdadm, partitioned array

[Fab <azertyzero@free.fr>]

 <michael <at> estone.ca> writes:

> Running some bonnie++ benchmarks gave extra slow write results on
> /dev/md_d0p1.
> but the same tests on /dev/md_d0p2 are normal. Read results are approx
> the same on both partitions, but only writes are half as fast on p1
> then p2.

Same problem. But I wasn't as bad as you with my benchmarks. I had ~100MB/s
on the second partition and about 72MB/s on the first one.

> I'm not quite sure why I'm getting these results. Any ideas to
> what could be wrong, or what to look for?

What could be wrong : no.
What to look for : yes.

Try to make your first partition to begin at cylinder 2 instead of cylinder
1 (with fdisk, or whatever).

-----

About using LVM, I really couldn't get the same performance than with
partitions :

I tried a lot of different configurations when I made my logical volumes,
but none worked. Does someone have an idea about what could be wrong ?

Thanks :)

Here are my benchmarks :



# dd if=/dev/md0 of=/dev/null bs=100M count=20
20+0 records in
20+0 records out
2097152000 bytes (2.1 GB) copied, 9.58494 seconds, 219 MB/s

dd if=/dev/raidvol1/data1 of=/dev/null bs=100M count=20
20+0 records in
20+0 records out
2097152000 bytes (2.1 GB) copied, 12.396 seconds, 169 MB/s

# dd if=/dev/raidvol1/data2 of=/dev/null bs=100M count=20
20+0 records in
20+0 records out
2097152000 bytes (2.1 GB) copied, 13.4758 seconds, 156 MB/s

# dd if=/dev/raidvol1/home1 of=/dev/null bs=100M count=20
20+0 records in
20+0 records out
2097152000 bytes (2.1 GB) copied, 17.7541 seconds, 118 MB/s