Re: Degraded raid handling

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On 5/21/07, Phillip Susi <psusi@xxxxxxxxxx> wrote:
It could happen that the bios sees both disks just fine, but for
whatever reason, the kernel only sees one.  In that case, dmraid will
activate the set with just the one disk, but without updating the
metadata to indicate this has been done, the set will be corrupted at
the next boot.  Not good...

Already happened here, I think... I have my two disks mirrored on an
"Intel Corporation 82801GR/GH (ICH7 Family) Serial ATA Storage
Controller AHCI". From the grub prompt I can browse (hd0,2) and
(hd1,2) and I can see there's a difference between them. The BIOS tool
says everything is fine (and there's no option to repair).

The damage was probably caused either by playing with udev rules or by
having savedefault in the grub menu.lst.

$ sudo dmraid -s
*** Group superset isw_dhedigiiib
--> Active Subset
name   : isw_dhedigiiib_osmoraid
size   : 488390656
stride : 256
type   : mirror
status : ok
subsets: 0
devs   : 2
spares : 0

$ sudo dmraid -r
/dev/sda: isw, "isw_dhedigiiib", GROUP, ok, 488397166 sectors, data@ 0
/dev/sdb: isw, "isw_dhedigiiib", GROUP, ok, 488397166 sectors, data@ 0

$ sudo dmraid -b
/dev/sda:    488397168 total, "S09QJ10YB19706"
/dev/sdb:    488397168 total, "S09QJ10YB19699"

$ sudo dmraid -tay
isw_dhedigiiib_osmoraid: 0 488390656 mirror core 2 131072 nosync 2
/dev/sda 0 /dev/sdb 0
ERROR: opening "/dev/.static/dev/mapper/isw_dhedigiiib_osmoraid"

What does "nosync" mean? I get the same on another machine where I
thought everything was fine though.

However, I wonder if I screwed up when I chose AHCI in the BIOS before
installing - I thought it meant ahci+raid - the OS'es think I am
running RAID, but I am not sure about the BIOS. (XP sees only the raid
volume so it seems to work fine, but the Intel Management Console does
not say anything about RAID, just lists the two disks. And grub sees
two disks.)

Tormod

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