Hi list,
I would like to understand if, and why, the --unsafe flag is needed when
using --copy-storage-all when migrating guests which uses writeback
cache mode.
Background: I want to live migrate guests with writeback cache from host
A to host B and these hosts only have local storage (ie: no shared
storage at all).
From my understanding, --unsafe should be only required when migrating
writeback-enabled guests between two hosts which share non-cluster-aware
storage (ie: NFS), but it should not be necessary when not sharing storage.
However, when trying to migrate from a CentOS6 host to a CentOS7 machine
with command
[root@source ~]# virsh migrate Totem --live --copy-storage-all
--persistent --verbose qemu+ssh://root@172.31.255.11/system
I have the following error:
error: Unsafe migration: Migration may lead to data corruption if disks
use cache != none
So, my questions are:
1) it is safe to do a live migration with --copy-storage-all when guests
are using writeback cache mode?
2) if so, why libvirt complains about that?
3) if not, what is the best method to migrate a running quest using
writeback cache mode?
Thanks.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@xxxxxxxxxx - info@xxxxxxxxxx
GPG public key ID: FF5F32A8
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