On Sun, Jan 10, 2016 at 06:07:33PM +0800, Luo Gangyi wrote: > Hi devs, > > > Do you test the difference between within and without > VIR_MIGRATE_NON_SHARED_INC ? > > > When I add VIR_MIGRATE_NON_SHARED_INC in block_migration_flags in > nova, nova block migration behaves more like a full copy of disk. The > disk in destination nodes is large(10GB+) and the process of live > migration is slow. > > > However, when I remove VIR_MIGRATE_NON_SHARED_INC in > block_migration_flags in nova, nova block migration behaves more like > a incremental copy of disk. The disk in destination nodes is > small(10MB-) and the process of live migration is very fast. > > > So I was confused about what VIR_MIGRATE_NON_SHARED_INC really means.
There are two flags that are related, that might be helpful to be clear about: VIR_MIGRATE_NON_SHARED_DISK and VIR_MIGRATE_NON_SHARED_INC. Below is an explanation[1] with example, by Eric Blake, from libvirt-users list. NB: It is talking in terms of `virsh` commands, where '--copy-storage-all' means VIR_MIGRATE_NON_SHARED_DISK and '--copy-storage-inc' means VIR_MIGRATE_NON_SHARED_INC: "If you use qcow2 backing chains for thin provisioning, as in: base.qcow2 <- active.qcow2 then --copy-storage-all copies the entire disk over to the destination (both base.qcow2 and active.qcow2 contents), while --copy-storage-inc copies only active.qcow2 (and assumes you have manually copied base.qcow2 in some other means - since it is read-only, it won't change from the last migration, and there are some storage arrays where you can very efficiently copy files around). Thus, --copy-storage-inc can be MUCH faster if active.qcow2 represents a small delta in relation to base.qcow2." [1] https://www.redhat.com/archives/libvirt-users/2015-April/msg00172.html Semantics of "virsh migrate --copy-storage-all" vs. --copy-storage-inc -- /kashyap __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev