Xen users - Feb 2006 - problems accessing unused physical hard drives from Dom0

Hi,

I run an Ubuntu Breezy Dom0 under Xen 3.0.1 (official Xen 2.6.12.6
kernels from xen-3.0.1-install.tgz). In the machine i''ve got 2 IDE ATA
discs, hda and hdc. The Dom0 runs on hda1 (a big / partition), hda2 is
swap. hdc is totally unused (an empty disc, exactly the same model that
hda).

8 to 10 domU run from .img files located in /vserver without problems
(unmodified kernel 2.6.12.6-xenU).

I''d like to make a mirror (backup) of hda on hdc, in case anything goes
wrong. I have a script which recreates hda''s partitions on hdc, format
them, then rsync hda* on hdc* (basically). this script works on a non
Xen machine (it is used on our 5 production servers).

The problem is that whenever the script tries to access hdc* under the
Dom0, the kernel reports "device busy".

sfdisk can''t create the partition table, but if i --force it, it does.
mkfs.ext3 won''t format hdc1, but if I -F it, it will. But mount refuses
to mount the partition because of "device busy or already mounted",
which is obviously wrong (nothing related to hdc
in /etc/fstab, /etc/mtab or /proc/mounts in the Dom0...).

I tried searching for this in the Xen-users mailing list archives, but
didn''t find anything relevant (didn''t try the bugtracker or
Xen-devel
archives, feel free to redirect me if this is a known issue)... Any
advice will be appreciated, on finding why i can''t access /dev/hdc
under
the Dom0, and resolving the problem too ;)

Booting the Dom0 without Xen (in "native linux kernel mode") makes the
problem dissapear, but i''d like to do the backup without rebooting the
machine (just shutting down the DomU''s)...

all relevant informations about the machine (dmesg, xen dmesg,
dmidecode, send-config and such) can be found at
http://deep-ocean.net/files/xen/ . It some info is missing, ask me i
will put it there or on the list.

best regards and thanks in advance,

Olivier Cortès


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