Comment 24 for bug 372170

> This is actually the metadata being moved to a different location so dmraid cant find it.

Right, the metadata is being moved by the HPA, so when the kernel disables HPA, dmraid can't find the metadata any more.

With default settings (Ubuntu 9.04, 2.6.28-11-generic #42-Ubuntu SMP Fri Apr 17 01:58:03 UTC 2009 x86_64 GNU/Linux since I didn't specify before), my drives both look like this:
---
$> sudo fdisk -l -u /dev/sda

Disk /dev/sda: 251.0 GB, 251000193024 bytes
255 heads, 63 sectors/track, 30515 cylinders, total 490234752 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0xb782b782

   Device Boot Start End Blocks Id System
/dev/sda1 * 63 490207409 245103673+ 7 HPFS/NTFS
----

and dmraid can only find the metadata on /dev/sdb

With 'libata.ignore_hpa=0' in the kernel command line, I get

---
$ sudo fdisk -l -u /dev/sda

Disk /dev/sda: 250.9 GB, 250999111168 bytes
255 heads, 63 sectors/track, 30515 cylinders, total 490232639 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0xb782b782

   Device Boot Start End Blocks Id System
/dev/sda1 * 63 490207409 245103673+ 7 HPFS/NTFS

$ sudo fdisk -l -u /dev/sdb

Disk /dev/sdb: 251.0 GB, 251000193024 bytes
255 heads, 63 sectors/track, 30515 cylinders, total 490234752 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0xb782b782

   Device Boot Start End Blocks Id System
/dev/sdb1 * 63 490207409 245103673+ 7 HPFS/NTFS
---

with 2113 fewer total blocks on /dev/sda, and dmraid finds the metadata on both disks.