Change in ataraid (geometry?) between RELENG_5 and RELENG_6?

[Andrew Reilly]

Hi,

I just tried to do an in-place upgrade from RELENG_5 to RELENG_6
on a system that was running an ataraid mirror on a pair of SATA
disks.  The root file system (256M) mounted fine, but fsck -p
fails (unable to find a superblock, from memory) under the new
kernel on my /usr partition, which is about 73G (most of the 80G
of the disks).  Falling back to the RELENG_5 /boot/kernel and
fsck finds no problem.

Is there a known behaviour change in ataraid behaviour between
the two versions?  The hardware is Intel P4, ICH6 SATA150, and a
pair of Seagate 80G SATA drives.

One odd-looking thing that I've just noticed (in RELENG_5, of
course) is that fdisk ar0 says that cylinders=9729 heads=255
sectors/track=63, but fdisk ad4 (the first of the "real" SATA
disks) says cylinders=155061, heads=16, sectors/track=63.
Should these really be so different?

Is backup and start again from label/newfs my only option?

Cheers,

-- 
Andrew