Re: Speed drop /dev/sda -> /dev/sda1 -> /dev/vg0/test (3ware/LVM)

["Miquel van Smoorenburg" <miquels@cistron.nl>]

In article <20031229125412.GA28262@cistron.nl>,
Miquel van Smoorenburg  <miquels@cistron.nl> wrote:
>Hello,
>
>	I'm running Linux 2.6.0 with a 3ware 8506 controller in
>hardware RAID5 mode. The RAID5 array is built of 7+1 200 MB SATA
>disks.
>
>Now it appears that more "mappings" on the array have a bad
>influence on speed. /dev/sda is the fastest, /dev/sda1 is quite
>a bit slower, LVM on /dev/sda is slower yet and LVM on /dev/sda1
>is the slowest.

For reference, I just took 2.4.24-pre2, applied the device-mapper
patches to it, and re-ran the tests.

Base performance on /dev/sda is a bit slower (70 MB/sec vs 80 MB/sec
raw writespeed), but speeds on /dev/sda1 and /dev/vg0/test are
exactly the same.

So it doesn't look like a 3ware driver or LVM issue as those are
basically the same between the 2.4 and 2.6 systems.

Mike.
-- 
When life hands you lemons, grab the salt and pass the tequila.