[Xen-users] Re: Mounting domU filesystem on Dom0. (xm mount)

[Ligesh <myself@xxxxxxxxxx>]

On Wed, Mar 14, 2007 at 02:23:40PM +0200, Siim Vahtre wrote:
> >LVMs are not the solution. You need the domU kernel's help to do 
> >anything without completely ruining the filesystem. Currently, I think 
> >the best way would be customize a simple nfsd for this purpose.
> 
> Remember that if you backup directly from filesystem (or from NFS export 
> or whatever), the filesystem contents can change even while you're backing 
> up! That doesn't happen with LVM.
> 
> To get "really" consistent backup, the backup software must cooperate with 
> the application, which can be quite complicated. But if the application is 
> written well, it should be able to handle poweroffs, at least as far as 
> not completely destroying your data.
> 
> LVM is far from perfect, but I wouldn't say it is "terrible terrible" for 
> your task.

 With LVM, you get filesystem (kernel) level corruption. With nfs, you get 
application level corruption. The first is obviously graver. There's real world 
proof too. Openvz uses the latter kind of backup, and we have a lot of 
customers who are using it for centralized backup of their entire vps farm, and 
I havne't had any real problem with. Unlike the LVM based one which actually 
made the entire system unusable twice.

 Thanks.



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