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

[Ligesh <myself@xxxxxxxxxx>]

On Wed, Mar 14, 2007 at 01:13:15PM +0200, Siim Vahtre wrote:
> >I have raised this thing many times in myriad different ways, and to me, 
> >Xen still seem to lack the ability to access the domUs in a proper 
> >manner so as to allow mass management of the domUs, and one of the 
> >important things here is backup. If you have to manage 1000 domUs across 
> >50-60 machines, then it would be essential to be able to take backup of 
> >the entire system.
> 
> Why not use LVM snapshots? I use snapshot feature to backup domU's from 
> dom0 and I am very satisfied.

 LVM Snapshots are terrible terrible idea. You are basically mounting an 
inconsistent file system that has not yet been synced, and I am sure you have 
never tried to restore the backups you have so conscientiously taken. Believe 
me one day, if you try to restore the backup, it will completely ruin your 
system. The LVM snapshot is the state of a filesystem that's running, and it is 
equivalent to powering off the system. And at the least, you should run e2fsck 
on the LVM before you actually tar it up.

> 
> >This actually can be achieved even on normal Xen system, by running an 
> >nfs daemon and exporting the '/' to the dom0, which can then be mounted 
> >and backedup, like any live system.
> 
> And why not use it?

 The point is that I can't enable nfs on 1000 domUs. That's another problem 
with xen. On openvz, I can do for in in `vzlist` ; do vzctl exec 
/etc/init.d/nfs restart done. How do I do it on xen? But even if this were 
possible,  nfs is too heavy, and it is insanity to have 1000 nfses running on 
your system. That is a most callous waste of memory, multiplied a 1000 times.

[quote] 
> 
> You can also use shared filesystems like GFS or OCFS2.
[/quote] 

 I will try that out. It _appears_ to be a possible solution, if only due to 
the fact that, it is the only one I haven't yet tried and found major problems 
with.



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