[Pkg-xen-devel] (re-titled) partitions and LVs

[Daniel Pocock]

On 20/12/08 19:05, Ian Campbell wrote:
> On Sat, 2008-12-20 at 16:29 +0000, Daniel Pocock wrote:
>> My only other concern with the domU is that it has partitioned an LVM 
>> volume, and grub installed to the MBR.  That makes it more awkward to 
>> mount the LVM volume from dom0 (although not impossible).  Should I have 
>> used
>>
>> disk = ['phy:vg00/th2_root,xvda1,w']
>>
>> instead of
>>
>> disk = ['phy:vg00/th2_root,xvda,w']  ?
>>
>> Would the grub install work with the latter approach?
> 
> I don't like that way myself but I think it would work, the installer
> might be confused during the partitioning phase I guess.
> 
> I use kpartx in dom0 which makes is reasonably simple to mount the
> individual partitions of an LVM device.
> 

Can anyone comment on whether both approaches are still generally
considered to be valid, and/or, in which situations?

My current understanding of the issue:

Benefits of having a partition table on the LV used by the domU:
- some software seems to expect this
- better for situations where each domU has a distinct sys admin (e.g. a
virtual hosting provider where each domU is owned by a different customer)
- better for SANs and iSCSI with many volumes and servers, as the
partition table serves as a kind of label to help identify the filesystem
- domU /etc/fstab can have meaningful device (LV) names if a nested VG
is used

Benefits of giving the domU a different dom0 LV for each of it's
filesystems:
- easier to mount/administer from the dom0 (no need for kpartx and
vgimport, lvchange, etc)
- easier to move individual LVs between different domUs (whereas
resizing a partition requires a domU reboot)
- easier to resize (expand or shrink) individual LV allocations on the
dom0s VG (consequently more space efficient)