[libvirt-users] Unsafe migration with copy-storage-all (non shared storage) and writeback cache

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(a)assyoma.it - info(a)assyoma.it GPG public key ID: FF5F32A8