Re: Why do arrays start without some components?

On Mon, Mar 15, 2010 at 1:26 PM, Simon Matthews
[off-list ref] wrote:

On Mon, Mar 15, 2010 at 2:04 PM, Asdo [off-list ref] wrote:

quoted

Simon Matthews wrote:

quoted

I have a couple of machines on which this is happening now --

When the machine boots, the RAID arrays (RAID 1) start, but each array
only has one component device. I can add the other component again
(using mdadm --add ... ) and the array will sync up, but next time it
boots, I have to do the same once more.

Why is this and how do I fix it?

Might that be a /etc/mdadm/mdadm.conf in the initramfs listing fewer devices
than it should?
I am not sure (because in this case maybe it shouldn't autoassemble the
array at all), but have a look by unpacking your initramfs. If yes, update
it.

I don't have an initramfs. This is a Gentoo system and I built the
kernel with all the drivers required to boot built in. This includes
RAID support.

quoted

Or could that be a controller that shows the disks to the kernel too late...
do you have multiple controllers?

I don't think so, on one machine they are SATA drives, but only one controller.

But, perhaps on the other machine, this may be happening, since the
drive that includes the component that is left out of the array is on
an add-in controller. On this machine, the problematic array uses IDE
drives for its components.

Replying to my own email -- bad form, I know. However, some additional
information. The components that do form the degraded array on boot up
on the all-SATA machine are all /dev/sdbX and the missing components
are all /dev/sdaX. I think this makes it unlikely that the controller
is showing the disks to the kernel too late, since I think it is
likely that the /dev/sdaX disks are shown first.

Simon