Re: [Xen-users] increase size for dom guest using lvm online

["Thaddeus J. Hogan" <thaddeus@xxxxxxxxxx>]

> At the moment, I believe the size passed to the guest is fixed at 
> creating time, so if you enlarge the volume, the guest won't get to 
> know about it until it is shut down and re-created.
I just verified that this is the case on Xen 3.2 on Debian 5.  I was not 
able to get the guest to pick up the change in device size.
There is the option of doing LVM in the guest, though this will make the 
volumes more difficult to access from the Xen dom0.  If you do lvm in 
the guest you will be able to attach a new chunk of disk, then run 
pvcreate on it and add it to a volume group in your guest.  However if 
the dom0 is running lvm as well it will try to register the volume 
groups defined by the PVs that you are intending to map through to your 
guests.  You have two options for preventing this from creating problems 
on the dom0.  First, you could exclude from the scan process in lvm.conf 
those devices destined to be used with LVM in a guest, but you will not 
be able to mount these volumes in the dom0 as a result.  The other 
option is to name your volume groups differently for every guest so 
there are no conflicts when lvm in the dom0 does a pvscan, this allows 
you to use the volumes from dom0 but can be a manageability issue.
Personally I don't think the tradeoffs are worth it for online resize.  
I do my LVM on the dom0 and then send individual LVs to the guests as 
xvda, xvdb, etc. but I cannot resize these without a reboot.
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