RE: [Xen-users] Xen 4.0 feature request

[Nathan Eisenberg <nathan@xxxxxxxxxxxxxxxx>]

Enrico,

Why can't you save only one VM with LVM snapshots?  Sounds like you have an odd 
implementation, rather that there being a problem with LVM.  We export two LVs 
per domU - 1 'data' and 1 'swap'.  I can easily snapshot the 'data' LV of any 
single domU without a performance problem.

LVM snapshots are exactly what you're looking for.  However, for real backups, 
I always recommend that you start with an 'inside' approach, and treat the domU 
like any other server.  

In my experience, buying solely into the 'snapshot as a backup' idea is a one 
way ticket to lost data.

Best Regards
Nathan Eisenberg
Sr. Systems Administrator
Atlas Networks, LLC
support@xxxxxxxxxxxxxxxx
http://support.atlasnetworks.us/portal


-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Enrico Valsecchi
Sent: Monday, July 06, 2009 7:38 AM
To: Eljas Alakulppi
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Xen 4.0 feature request

Eljas,
if you have a very large filesystem (some TB) and use a clustered 
filesystem (ex: lustre),
for performance reason isn't a good solution work with LVM....
....and, if you want save only one virtual machine, you can't use a LVM 
snapshot technology!

I think that xen must have a tools that allow create a consistent 
snapshot, because
are a unique possibility to have this features in any environment.

O.K., I mean that this are required only in a enterprise environment but,
if XEN want are a very powerfull vmware alternative, I think that some 
tools are indispensable!

Bye,

Enrico

> If you want snapshots of the filesystem, use LVM. "xm save" takes 
> snapshot of the domain's state (memory and such).
>
> One secnario where xm save is useful: You need to reboot the Dom0, but 
> want to restore DomUs back to how they were after reboot (really 
> useful when your router is in DomU. Reboot is normally fast enough to 
> get the router back up before the connections timeout).
>
> -Eljas Alakulppi
>
> On Sun, 05 Jul 2009 17:35:54 +0300, Enrico Valsecchi 
> <admin@xxxxxxxxxx> wrote:
>
>>> Do you know "xm save"?
>>>
>>> Overmind # xm save
>>> Error: 'xm save' requires between 2 and 3 arguments.
>>>
>>> Usage: xm save [-c] <Domain> <CheckpointFile>
>>>
>>> Save a domain state to restore later.
>>>   -c, --checkpoint               Leave domain running after creating
>>
>> Yes,
>> I know xm save command....
>> ....but:
>>
>> I have make a snapshot with xm save -c, then I have delete some file 
>> in a
>> system
>> (complete remove /boot directory)
>> O.K., I'm shutdown domain and restore.
>>
>> Result are that domain start, but does not are file deleted from me!
>>
>> My little and stupid question are:
>>
>> What do you do with this snapshot???????
>>
>> Bye,
>>
>> Enrico
>>
>> _______________________________________________
>> Xen-users mailing list
>> Xen-users@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-users
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users
>
>


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