> > Message: 20 > Date: Mon, 17 Mar 2014 16:05:17 +0100 > From: Sebastien Han <sebastien....@enovance.com> > To: "Don Talton (dotalton)" <dotal...@cisco.com> > Cc: "ceph-users@lists.ceph.com" <ceph-users@lists.ceph.com> > Subject: Re: [ceph-users] qemu non-shared storage migration of nova > instances? > Message-ID: <86ed699a-de8b-4864-860f-e324a6f11...@enovance.com> > Content-Type: text/plain; charset="windows-1252" > > Hi, > > I use the following live migration flags: > VIR_MIGRATE_UNDEFINE_SOURCE,VIR_MIGRATE_PEER2PEER,VIR_MIGRATE_LIVE,VIR_MIGRATE_PERSIST_DEST > It deletes the libvirt.xml and re-creates it on the other side. >
We use this setup (local direct-attached ephemeral storage and Ceph for persistent volumes) in a production OpenStack cloud. The biggest problem (which I think is still present with newer Qemu&Libvirt, though we are on 1.0 and 1.1.1 respectively at the moment) with this is that live-block-migrations copy all block device contents from source to destination... i.e., even volumes get transferred in a ridiculous sequence of "source hypervisor reads blocks from storage cluster -> source hypervisor streams blocks to destination hypervisor -> destination hypervisor writes blocks back to the storage cluster". Is that something others have run into and found workarounds for? -- Cheers, ~Blairo
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