[Ovirt-devel] Save/Resume Issues

[Chris Lalancette]

Ian Main wrote:
> 
> Howdy Folks :)
> 
> So in my working with taskomatic, I noticed that the save/resume
> functionality seems a bit broken.  The first thing I noticed was that libvirt
> itself has no concept of a separate state for 'saved', which ovirt attempts
> to maintain.  This could work fine but when a node is disconnected and then
> reconnected, the state will shift to 'unavailable' and then to 'stopped' when
> it reconnects.  There may be other corner cases where this does not work as
> well.
> 
> The other issue is that it saves the image to /tmp on the local node.  This
> is usually (always?) a memory based FS and so it will be lost on reboot of
> the node.  It also does not allow for resume on a different host, and
> presently is not removed after resume so the FS will eventually fill up with
> a few save/resume cycles.
> 
> To fix all this I'm thinking we should save our images on a designated
> storage device, using a new field in the vm database to denote that it is
> saved, perhaps with the path to the saved image.  Once restored or started
> the image should be deleted.

Yes, sorry, Jim and I had a discussion about this on IRC the other day, I should
have sent mail.  You are basically exactly right; in it's current incarnation
save/restore is 100% completely broken.  Basically, we need what you say; the
user needs to configure a "save pool" (probably per hardware pool), and then on
a save we write to that pool, and store something in the database with a pointer
to the filename.  On a restore, we read that filename back, restore the image,
and delete the restore file.  I'm sure there are state problems like you point
out as well.


-- 
Chris Lalancette