From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: organizing virtual machines Date: Mon, 21 Feb 2005 17:35:57 -0600 Message-ID: <421A705D.9020604@codemonkey.ws> References: <421A667D.4030507@harvee.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit In-Reply-To: <421A667D.4030507@harvee.org> Sender: xen-devel-admin@lists.sourceforge.net Errors-To: xen-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: "Eric S. Johansson" Cc: xen-devel@lists.sourceforge.net List-Id: xen-devel@lists.xenproject.org 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@codemonkey.ws ------------------------------------------------------- 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