50% speed penalty for LVM on mdraid

[Andy Burns]

> Wow that explains a lot.. performance on Development has be awful for me
> lately and I have been unable to figure out why, this might be related.
>
> My setup is 2 400GB drives in RAID0 using dmraid with LVM ontop.

It's a while since it tried dmraid instead of mdraid, does it use a
UUID as the PV name for /dev/mapper? I suppose pvdisplay would show,
then you could try hdparm on the PV under LVM compared to the LV above
it.