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

[Stanislav German-Evtushenko]

On Nov 19, 2014 7:23 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.

Stanislav
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