[Gllug] Detecting increase in underling disk size

[Andy Millar]

On Thu, 2009-05-14 at 12:23 +0000, James Hawtin wrote:
> Correct me if I am not understanding you correctely, hope this is a correct
> representation of your system.
> 
> SAN Lun0 -> host PV0 -> Host VG -> Host LV for guest -> Guest VM -> Disk -> LVM?

I'm pretty sure this looks correct.

> Add a new San lun into the Host VG then use the space to extend the Host LV?
> 
> SAN Lun0 -> host PV0 -> Host VG
> SAN Lun1 -> host PV1 -> Host VG -> Host LV for guest -> Guest VM -> Disk -> LVM?

Expanding the Host LV isn't the problem; this works fine. I've got a
large Host LV on the SAN running cluster LVM with plenty of free space.

The problem is getting the guest to detect the fact that the Host LV has
increased in size.

Some interesting output from the host:

  --- Logical volume ---
  LV Name                /dev/vg_san/domU_root
  VG Name                vg_san
  LV UUID                AstH5S-pEpx-Kjpf-RnVs-sazo-x0iz-OCkPui
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                11.00 GB
  Current LE             2816
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:11

# fdisk -l /dev/vg_san/domU_root

Disk /dev/vg_san/domU_root: 11.8 GB, 11811160064 bytes
255 heads, 63 sectors/track, 1435 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device                Boot   Start         End   Blocks   Id  System
/dev/vg_san/domU_root1   *       1          13   104391   83   Linux
/dev/vg_san/domU_root2          14        1435 11422215   83   Linux

and from the domU (guest) *after* I have resized the partition on the
dom0 (host):

# fdisk -l

Disk /dev/xvda: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device    Boot       Start         End      Blocks   Id  System
/dev/xvda1   *           1          13      104391   83  Linux
/dev/xvda2              14        1435    11422215   83  Linux

# partprobe 
Error: Can't have a partition outside the disk!

Andy
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