I have a system that has a large number of drives in it (45), and it's had
a problem with banks of disks getting disconnected from it.
however, when I started looking into it today (after another sysadmin
worked on it for a while), I found that the system is not able to access
the partitions on the drives.
if I am reading dmesg correctly it is seeing the partitions during boot,
and if I do 'fdisk -l' it lists all the paritions correctly, but if I try
to do a
dd if=/dev/sdb1 of=/dev/null count=1
I get the error "dd: opening `/dev/sdb1': No such device or address"
#ls -l /dev/sdb1
brw-rw---- 1 root disk 8, 17 Nov 7 2006 /dev/sdb1
I removed udev and setup nodes manually to eliminate any possibility that
it was a problem there.
the attachment partitions.missing.partitions is a cat of /proc/partitions
sysfs shows all the drives but none of the partitions.
if I run fdisk and do a write (which runs the ioctl to re-read the
parition table) the system detects the partition and is able to access it
until the next reboot.
what is going on here?
David Lang
I managed to track the problem down.
it turns out that at some point someone created a md array using the raw
devices instead of the partitions. it looks like the kernel autodetection
for raid kicked in prior to the partition detection and after it claimed
the drives the partition detection was never given a chance to do so.
this is logical, but it makes the dmesg output that appears to be
identifying the paritions _very_ misleading.
David Lang
On Wed, 8 Jul 2009, [email protected] wrote:
> Date: Wed, 8 Jul 2009 14:35:41 -0700 (PDT)
> From: [email protected]
> To: linux-kernel <[email protected]>
> Subject: partition detection problem on 2.6.29.1 and 2.6.30
>
> I have a system that has a large number of drives in it (45), and it's had a
> problem with banks of disks getting disconnected from it.
>
> however, when I started looking into it today (after another sysadmin worked
> on it for a while), I found that the system is not able to access the
> partitions on the drives.
>
> if I am reading dmesg correctly it is seeing the partitions during boot, and
> if I do 'fdisk -l' it lists all the paritions correctly, but if I try to do a
>
> dd if=/dev/sdb1 of=/dev/null count=1
>
> I get the error "dd: opening `/dev/sdb1': No such device or address"
>
> #ls -l /dev/sdb1
> brw-rw---- 1 root disk 8, 17 Nov 7 2006 /dev/sdb1
>
> I removed udev and setup nodes manually to eliminate any possibility that it
> was a problem there.
>
> the attachment partitions.missing.partitions is a cat of /proc/partitions
>
> sysfs shows all the drives but none of the partitions.
>
> if I run fdisk and do a write (which runs the ioctl to re-read the parition
> table) the system detects the partition and is able to access it until the
> next reboot.
>
> what is going on here?
>
> David Lang