[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] Design session report: Live-Updating Xen



On 17.07.19 00:27, Andrew Cooper wrote:
On 16/07/2019 05:20, Sarah Newman wrote:
On 7/15/19 8:48 PM, Juergen Gross wrote:
On 15.07.19 21:31, Sarah Newman wrote:
On 7/15/19 11:57 AM, Foerster, Leonard wrote:
...
A key cornerstone for Live-update is guest transparent live migration
...
     -> for live migration: domid is a problem in this case
         -> randomize and pray does not work on smaller fleets
         -> this is not a problem for live-update
         -> BUT: as a community we shoudl make this restriction go away

Andrew Cooper pointed out to me that manually assigning domain IDs
is supported in much of the code already. If guest transparent live
migration gets merged, we'll look at passing in a domain ID to xl,
which would be good enough for us. I don't know about the other
toolstacks.

The main problem is the case where on the target host the domid of the
migrated domain is already in use by another domain. So you either need
a domid allocator spanning all hosts or the change of domid during
migration must be hidden from the guest for guest transparent migration.

Yes. There are some cluster management systems which use xl rather
than xapi.
They could be extended to manage domain IDs if it's too difficult to
allow
the domain ID to change during migration.

For a v1 feature, having a restriction of "you must manage domids across
the cluster" is a fine.  Guest-transparent migration is a very important
feature, and one where we are lacking in relation to other hypervisors.

Longer term, we as the Xen community need to figure out a way to remove
the dependency on domids, at which point the cluster-wide management
restriction can be dropped.  This isn't going to be a trivial task, but
it will be a worthwhile one.

Another problem are Xenstore watches. With guest transparent LM they are
lost today as there is currently no way to migrate them to the target Xenstore.

Live-Update could work around this issue via Xenstore-stubdom.


Juergen

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.