Re: [Qemu-block] [PATCH COLO v3 01/14] docs: block replication's description

[Dr. David Alan Gilbert]

* Stefan Hajnoczi (address@hidden) wrote:
> On Fri, Apr 24, 2015 at 11:36:35AM +0200, Paolo Bonzini wrote:
> > 
> > 
> > On 24/04/2015 11:38, Wen Congyang wrote:
> > >> > 
> > >> > That can be done with drive-mirror.  But I think it's too early for 
> > >> > that.
> > > Do you mean use drive-mirror instead of quorum?
> > 
> > Only before starting up a new secondary.  Basically you do a migration
> > with non-shared storage, and then start the secondary in colo mode.
> > 
> > But it's only for the failover case.  Quorum (or a new block/colo.c
> > driver or filter) is fine for normal colo operation.
> 
> Perhaps this patch series should mirror the Secondary's disk to a Backup
> Secondary so that the system can be protected very quickly after
> failover.
> 
> I think anyone serious about fault tolerance would deploy a Backup
> Secondary, otherwise the system cannot survive two failures unless a
> human administrator is lucky/fast enough to set up a new Secondary.

I'd assumed that a higher level management layer would do the allocation
of a new secondary after the first failover, so no human need be involved.

Dave

> Stefan


--
Dr. David Alan Gilbert / address@hidden / Manchester, UK