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

[Michael Hohnbaum <hohnbaum@xxxxxxxxxx>]

On Wed, 2005-01-26 at 14:01 -0600, Anthony Liguori wrote:
> On Wed, 2005-01-26 at 13:11, Andrew Warfield wrote:
> > > 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?
> > 
> > No.  There has been no discussion of storing suspended domains.  For
> > the moment, i think it's probably best to design the store to contain
> > runtime state for the currently executing set of VMs on the physical
> > host.  So records in the store are persistent across daemon restarts,
> > and dom0 restarts.
> 
> Excellent!  Then I have no worries at all about it.
> 
> You mentioned the current design looks a lot like a file system, any
> thoughts on actually using the file system?  Either within the normal
> file system (within something like /var/xen/<domid>) or as a pid-like
> /proc entry (like /proc/xen/<domid>).

Wouldn't want to do this in the kernel (i.e., /proc or /sysfs) as it
would not be persistent across dom0 restarts.  In a regular filesystem
as {directories, subdirectories, files} would be reasonable.  In either
case, persistent store would need to determine whether the entire
system (Xen) has restarted, dom0 has restarted, or just the xend has
restarted and clean up residual info appropriately.

While beyond the current focus, persistent store could feasibly
be used to hold domain definitions for non-existent domains and 
suspended domains.  One could envision adding a state field into
the domain configuration/definition.  Valid states for current 
capabilities would be {active, suspended, migrated, inactive}.  On
the other hand, keeping persistent store info on only active domains
in this mechanism and moving info to higher level tools about predefined
domains, suspended domains, etc. would work.  It's a tradeoff between
similar info being maintained in multiple places, or added complexity
in a single place.

                      Michael
> 
> Regards,
-- 
Michael Hohnbaum                             503 578 5486
hohnbaum@xxxxxxxxxx                          t/l 775 5486



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