Re: [PATCH] xenctld - a control channel multiplexing daemon

[Anthony Liguori <aliguori@us.ibm.com>]

On Wed, 2005-01-26 at 08:33, Andrew Warfield wrote:
> Having the store worked in properly should 1. make rebooting dom0 with
> active VMs unaffected more possible, 2. make adding new functionality
> (e.g. new split device types) more straightforward, and 3. make
> writing tools that need state information, and 4. scaling control up
> to a cluster all a lot more tractable.

It seems like there's two distinct problems.

1) Managing domain specific state for running domains.

This can be done easily enough since a domid is a unique identifier. 
Any associative database would work just fine.

2) Managing domain specific state for non-running domains.

Since non-running domains have to have some sort of disk representation
(either a config file of some sort or a snapshot image) this also is
pretty easy.


I'm not convinced there's a great way to merge the two though.   It gets
really hairy once you start doing things like cloning or migration. 
There's a lot of subtle things like reassigning MAC addresses that gets
nasty.

In reality, what's the different between a domain that's suspended to
disk and a clone domain that just hasn't been started yet.

Does the current persistent store architecture attempt to solve this
problem?  Does it attempt to solve both problems?

I'd like to see a persistent store that just addressed problem #1.  I
think once you get into trying to solve #2, you'll create a solution
that won't work for everyone.

I'd like to see Xen with a tool that can create domains from a
configuration file but at the same time, it would be nice if the
persistent store worked well with domain's that are created by hand.

Regards,

-- 
Anthony Liguori
Linux Technology Center (LTC) - IBM Austin
E-mail: aliguori@us.ibm.com
Phone: (512) 838-1208




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