Re: [Xen-users] Re: Mounting Xen LVM Guests

["Fajar A. Nugraha" <fajar@xxxxxxxxx>]

On Wed, Jan 7, 2009 at 6:25 PM, Ferenc Wagner <wferi@xxxxxxx> wrote:
> "Fajar A. Nugraha" <fajar@xxxxxxxxx> writes:
>
>> Eredicator X wrote:
>>
>>> ----- "Fajar A. Nugraha" <fajar@xxxxxxxxx> wrote:
>>>
>>>> - learn how to use kpartx, pvscan, and vgscan, and hope you don't
>>>> have conflicting VG names.
>>>
>>> This is what I am currently trying to do.
>>
>> [...]
>>
>> IMHO, the steps above are painful. So I'd suggest that you reinstall
>> using only one partition (/) WITHOUT LVM, WITHOUT SWAP.
>
> In my experience, LVM inside domUs is very useful.

I find it a matter of preference and whom you get support from. I
believe RedHat's recommendation is :
- use dom0's HD, partition, or file as domU storage (not LVM)
- use LVM on domU

I prefer the other way around :
- use dom0's LV as domU storage
- use domU's disk directly without additional partitioning or LVM

Using LVM on both dom0 and domU, like what Eredicator is using, adds
something like 3% performance penalty.

> It makes
> persistent naming, snapshotting, live resizing or migration to new
> storage possible.  These may not count on a test system, but they do
> when you provide some important service via your domU.
>

In my case :
- persistent naming is done on dom0 using LVM. DomU always get the
same LV as hda1/xvda1.
- resizing is done by resizing dom0's LV. No live resize possible as
domU reboot required (or unmount and xm detach/attach)
- migration (I assume it's moving/copying domU to another dom0, not
live migration) can be done by copying dom0's LV contents
(snapshotting when necessary)

So I lost live resizing ability, but avoided the 3% performance
penalty. Plus, I get the ability to clone or rescue domUs easily.

> But then you should be familiar with the LVM tools anyway, so the
> above can't be a problem.

Correct.

> --
> YMMV

Agreed. Seems like LVM on domU works best for you.

Regards,

Fajar

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users