[Xen-users] Recursive LVM

["Ulrich Windl" <ulrich.windl@xxxxxxxxxxxxxxxxxxxx>]

Hi!

People are saying you shouldn't do it, but as it seems nice by cincept I did it:

Dom0 uses LVM to manage disk space, creating a large locical volume (LV) for 
each 
VM. I use the LV as a block device in DomU then, and DomU itself manages disk 
space using LVM, too.

People warned me that the VG (volume group) names must be unique, so I did 
that. I 
installed the system just fine, but when rebooting DomU, no root filesystem can 
be 
found:

...
bootloader = '/usr/lib/xen/boot/domUloader.py'
bootentry = 'hda1:/vmlinuz-xen,/boot/initrd-xen'
...

Traceback (most recent call last):
  File "/usr/lib/xen/boot/domUloader.py", line 505, in ?
    main(sys.argv)
  File "/usr/lib/xen/boot/domUloader.py", line 499, in main
    sxpr = copyKernelAndInitrd(fs, kernel, initrd)
  File "/usr/lib/xen/boot/domUloader.py", line 404, in copyKernelAndInitrd
    raise RuntimeError("domUloader: Filesystem %s not exported\n" % fs)
RuntimeError: domUloader: Filesystem hda1 not exported

Error: Boot loader didn't return any data!

When mounting the LV to another bootable VM, "fdisk -l" reports three 
partitions:
hda1 (/boot)
hda2 (swap)
hda3 (LVM, rest of the filesystems)

However the partitions have names like hda1p1 hda1p2 hda1p3

When I boot using another kernel, I get:

kernel = '/boot/vmlinuz-2.6.16.21-0.25-xen'
ramdisk = '/boot/initrd-2.6.16.21-0.25-xen'
root = '/dev/as1/root'

...

Loading xenblk
Registering block device major 3
 hda:Loading dm-mod
 unknown partition table
device-mapper: 4.5.0-ioctl (2005-10-04) initialised: dm-devel@xxxxxxxxxx
 hdb:Loading dm-snapshot
ata_id[473]: main: HDIO_GET_IDENTITY failed for '/dev/.tmp-3-0'
Waiting for /dev/mapper/control to appear:  ok
Loading reiserfs
  Unable to find volume group "as1"
Waiting for device /dev/as1/root to appear: .. unknown partition table
ata_id[497]: main: HDIO_GET_IDENTITY failed for '/dev/.tmp-3-64'
............................not found -- exiting to /bin/sh
[...]

Besides those problems, I wonder how I can loop-mount the LV the way XEN () 
does 
it:
  PID TTY      STAT   TIME COMMAND
20219 ?        S<     0:00 [xvd 14 07:00]
20220 ?        S<     0:00 [xvd 14 fd:00]

With 3.0.2 I made the bad experience that I can attach a block device to the 
Dom0, 
but I cannot detach it. Thus no DomU can use it until reboot. Kind of nasty 
bug...

Any cool hints? System is SLES10 on x86_64...

Regards,
Ulrich


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