Re: RE: [Xen-users] Backup solution

["Volker Badziong" <volker.badziong@xxxxxx>]

Hello,

AFAIK Windows writes away cached data after 5 seconds.

Otherwise I would recommend running a script calling "sync" inside the guest, 
then sync in dom0 (is this needed?), then make the LVM snapshot. The only 
problem is that there might be writes between the finished guest-sync and the 
not yet performed LVM snapshot. - How do backup software vendors quiesce the 
guest / VM? What is happening there besides the sync?

There is also the sync-tool from Sysinternals 
(http://www.microsoft.com/technet/sysinternals/FileAndDisk/Sync.mspx). Although 
this is stated to be written for removable devices, you might check if this 
also works for regular devices - and please report back here ;)

Regards, Volker.


> OK, but - if You create the LVM snapshot volume and make the backup of it,
> You assume the OS running in VM has written everything correctly to the
> logical volume and the logical volume is in consistent state. 
> But this assumption seems to be dangerous for me, especially by Windows
> DomU
> - how can You be sure, the OS hdd driver has written everything to the
> logical volume before You create the snapshot volume?
> 
> I would like also to use the LVM snapshots for backup, but this topic is a
> problem for me, which I could not solve yet...
> 
>       With regards
> 
>               Archie
> 
> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Fajar A.
> Nugraha
> Sent: Monday, July 02, 2007 11:52 AM
> To: xen-users
> Subject: Re: [Xen-users] Backup solution
> 
> Xin Chen wrote:
> > but LVM snapshot still has risk, must be survived from a  power
> failture.
> > correct me if i am wrong...
> > what I do now is shutdown, copy, start....
> >
> 
> Correct.
> However, for production system, you'd generally design a system that
> MUST be able to survive a power failure/hard reboot anyway. This means
> activating archive log (for Oracle), using Innodb (MySQL), using
> journaling filesystem, etc. So this shouldn't be an issue.
> 
> Reading Jordi's post I assume his priority was how to keep the VM during
> backups, so LVM snapshot should be a feasible solution.
> 
> Regards,
> 
> Fajar
> 
> > Fajar A. Nugraha wrote:
> >
> >> Jordi Espasa Clofent wrote:
> >>  
> >>
> >>> Hi all,
> >>>
> >>> We are planning to use XEN VPS in production environment. Before it we
> >>> need to design a realiable backup policy for obvious reasons. I view
> >>> two approaches:
> >>>
> >>> a) Use a "snapshot" system for backup ALL VM file (image).
> >>> b) Use a traditional backup system (rsync, tar, cpio) for backup
> >>> SELECTED data into VM.
> >>>
> >>> I prefer A option but I've read in this list it is not possible unless
> >>> you stop de VM during a few time (the time required for backup
> >>> operation itself).
> >>>   
> >>
> >> If your vm image are files, and use LVM snapshot, you don't need to
> STOP
> >> the VM for backup.
> >> This thread might help you :
> >>
> http://lists.xensource.com/archives/html/xen-users/2007-06/msg00688.html
> >>
> >> Regards,
> >>
> >> Fajar
> 
> 
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