Re: [Xen-devel] organizing virtual machines

[Anthony Liguori <anthony@xxxxxxxxxxxxx>]

Eric S. Johansson wrote:

> Every virtual machine must have effectively two partitions.  The first 
> being a root partition containing all of the system executables and 
> configuration files as well as the usual /var, /tmp, etc.  The second 
> being storage for your application/user.
This is one approach.  Not necessarily a perfect solution.

> Obviously, this seems like a terrible waste of space but given the 
> current dogs breakfast known as /etc, I'm not sure that is another 
> solution.  I have a few ideas on how to fix this that may or may not 
> pan out but not the hands (rsi).
There are really two other solutions that I know of.  Either some sort 
of content-addressable storage based file system (like Plan9's Venti) 
which would provide an optimum storage scenario (although at a 
performance/complexity cost) or some sort of Copy-On-Write filesystem or 
block device.
LVM snapshots has been suggested a COW mechanism.  The most appealing to 
me is something like UnionFS 
(http://www.fsl.cs.sunysb.edu/project-unionfs.html) however it's rather 
unstable and I don't think FiST is going in the kernel anytime soon.  
UnionFS does COW on a file-access level.  You have one read-only mount 
that's your root and if a file is changed, the read-only version is 
copied over to a read/write partition and that's used as the working copy.
A fantastic project for someone would be a from-scratch simplistic 
union-fs clone that could actually be integrated into the kernel.  Linux 
used to have such a filesystem (IFS) but it became unmaintained and 
eventually removed from the kernel.
Regards,

--
Anthony Liguori
anthony@xxxxxxxxxxxxx



-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.sourceforge.net/lists/listinfo/xen-devel