Re: AW: [Xen-users] snapshot - backup for xen vm's

[Chris Richardson <crichardson@xxxxxxxxxxxx>]

I run our images on a clustered fs ocfs2 to be exact and use a san to 
supply the space along with alowing me to share the fs between multiple 
servers. the reason i do this is live migration is a breeze using 
san/ocfs2 and using the sans internal snapshots provide backup.
-Chris

Xin Chen wrote:
> Thanks a lot! It really helps.
>
> Let me summarise some backup ideas here: (only for file-backed image 
> Dom U)
> Dom 0: LVM
> Dom U: file-backed image,  LVM inside Dom U.
>
> Backup dom U:
>
> idea 1:  given by Petersson Mats
>
> # xm save domU somefile
> # cp domU.img domU.img.bak
> # cp somefile somefile.bak
> # xm restore somefile
>
> note: save / restore for full-virtual is only available in Xen 3.10.
>
> idea 2: given by Fajar, correct me if I misunderstand.
>
> 1), assume I put all guest images in dom 0   /var/lib/xen/images       
> (image1, image2 ...) each image is a guest system.
> 2), make snapshot for /var/lib/xen/images.    question: if image1 is 
> 10G, image2 is 20G, how large the snapshot needs? 30G enough? I am 
> quit sure how snapshot works when it is a very big image file.
> 3), mount snapshot
> 4), copy image1 .... copy image2.......
> 5), umount
> 6), remove snapshot.
> question: the image1.bak actually is a backup of a running guest 
> system, when I start the system by this image1.bak, the system is 
> gonna be OK? It is like a reboot a running system, isn't it? correct 
> me. plz. or maybe some reference for my stupid question.
> ---
> compare: idea 1 seems easier to do, but the system would be 
> unavailable for 10 or more mins, copy 10G file isn't so quick.....
> idea 2 seems more complicate, but it make the system running 24 hours.
>
> Is there any better ideas for backing up xen guest file based dom U ? 
> please advise.
> Thanks a lot for all kind people in the xen-list.
>
> cheers,
> x
>
>
>
>
> Fajar A. Nugraha wrote:
>
> > Xin Chen wrote:
> >  
> >
> > > Does this snapshot backup idea work with image?
> > >
> > > I didn't put guest system as partition, I put them as image, one huge
> > > image. Does this backup way work with image?
> > >
> > >   
> > "backup from vm with mounting an archive nfs-server", like Josef did,
> > works pretty much for any kind of setup since you're doing backups from
> > domU (not 0). But in that case you don't create a snapshot first.
> >
> > An example whre this might be good, is if you only have small files
> > which rarely changed (think php web pages, config files, etc.).
> >
> > An example where this might be BAD :
> > - You have mysql or oracle
> > - Store data on LARGE datafiles (say several hundred MBs)
> > - Your database server is busy, accessed and updated all the time
> > - You "backup" the datafile by copying it to remote nfs server while the
> > db server is running
> > Which leads to unrecoverable, inconsistent database.
> >
> > My initial suggestion to Josef's question was to use LVMs for domU
> > storage, and use LVM snapshot to create a "consistent" view of the
> > filesystem at that time.
> >
> > If you use file-backed image domU, stored on domU filesystem, then you
> > can still use LVM snapshots. It just requires a few different steps.
> > Assuming your dom0 is stored on LVM (not partition):
> > - create an LVM snapshot of dom0's fileystem
> > - mount that snapshot
> > - backup your image from that snapshot
> >
> > Note that in this case you backup the entire domU HD image, and NOT
> > their content. If your domU uses LVM setup (inside the domU), then this
> > is pretty much the only option you have. You can backup the disk image,
> > but not the content directly.
> >
> > However,
> > If you use those file-based disk images as direct partitions on domU,
> > you can mount the file from that snapshot to get their content.
> > If your domU use partition setup (not LVM setup), you can use kpartx and
> > create block device entries.
> >
> >  
> >
> > > cause I don't wanna to save /restore everytime when I backup the guest
> > > system. It takes 10 mins downtime!
> > >
> > >   
> > You don't have to. Not if you just want to backup the disk image or its
> > content.
> > Regards,
> >
> > Fajar
> >
> >
> >  
> >
> > > cheers!
> > >
> > > it-news (Josef Lahmer) wrote:
> > >
> > >   
> > > > dear ralf schenk,
> > > > dear Fajar,
> > > >
> > > > i've useing the xensource installation iso which does lvm on dom0 by
> > > > default and i am quite happy with this installation.
> > > >
> > > > now i'm using backup from vm with mounting an archive nfs-server
> > > > store and copy the important files.
> > > >
> > > >     
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-users
> >  
>
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> http://lists.xensource.com/xen-users



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