Matt Darcy <kernel-lists@projecthugo.co.uk> wrote:
> Its almost as if there is an "IO leak" which is the only way I can think 
> of to describe it.the card / system performaces quite well as individual 
> disks, but as soon as its entered into a raid 5 configuration using the 
> any number of disks the creation of the array appears to be fine until 
> around %20-%30 through the assembly, the speed of the arrays creations 
> plummits and the machine hangs.

You have 7x250G disks in Raid-5, so that's 6x250G or 1.5T total space.
In the beginning of raid recovery, when the system is good, you're
getting 12M/s.  It slows then dies after 25% to 40% of completion.

6x250G is 1536000M, at 12M/s that's about 35 hours.  You tested the
disks individually (without Raid) for ~12 hours, which is about 34%
of 35 hours.  So it's possible you'd see the the same slowdown & hang
if you tested the individual disks longer.

You're having these problems on a Marvell controller with 2.6.15 and the
in-kernel sata_mv driver, right?  I've got a very similar system with
unexplained hard hangs too.  On my system the individual disks seem to
work fine, Raid-6 of the disks seems work fine, LVM of the disks seems
to work fine, but LVM of a Raid-6 of the disks hangs.

One wierd thing I've discovered is that if I enable all the kernel
debugging options, the system is perfectly stable, and all the debug
tests report no warnings or errors to the logs.  Seems like a race
condition somewhere, I'm suspecting in the interaction of Raid-6 and
LVM, but it could be anywhere I suppose.  I've attached the .config of
the production (non-debug) kernel that hangs, and the diff to the debug
kernel that works.


-- 
Sebastian Kuzminsky