[pve-devel] Default cache mode for VM hard drives

[Stanislav German-Evtushenko]

On Nov 19, 2014 9:34 PM, "Dietmar Maurer" <dietmar at proxmox.com> wrote:
>
> > > > AFAIK kvm live migration issues a disk flush, so that should not be
a problem?
> > > >
> > > > Out if sync blogs do not appear during migration, they appear under
normal
> > work
> > > > load.
> > >
> > > I do not really understand that. What do you mean by "Out if sync
blogs do not
> > appear during migration"?
> > Out of sync blocks are blocks that contain different data on two nodes.
Such
> > blocks appear when a VM just work under normal load and usually it
happens for
> > the area where VM's swap is placed. The longer VM is online, the more
out of
> > sync blocks appear. If we try to migrate such a VM online it will crash
because
> > data in VM's swap will be different after migration.
>
> Again, migration code flush all changes to disk, so there are no "out of
sync" blocks
> after migration. What do I miss?
>

These blocks are not in ram anymore and considered to be properly committed
while in fact they committed not property. Nothing to flush.

Stanislav
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.proxmox.com/pipermail/pve-devel/attachments/20141119/23c145dc/attachment.htm>