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From: | Jakob Bohm |
Subject: | Re: [Qemu-discuss] vm live storage migration with snapshots |
Date: | Wed, 11 Feb 2015 18:37:53 +0100 |
User-agent: | Mozilla/5.0 (Windows NT 6.3; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 |
On 11/02/2015 18:08, Edward Young
wrote:
Just a quick answer, others can answer on clever ways to transfer disk deltas between systems: - The usual way is to store both the base images and the deltas on some kind of shared storage accessible from both hosts involved in the migration, thus eliminating the need to transfer any disk contents. - To the extent that the (not changing at that point in time) base image and deltas for the non-current snapshot are stored in separate files, they could simply be transferred with ordinary tools such as cp, dd or rsync. - If you freeze execution of the guest during migration (not usually a preferred thing when wanting to do live migration), remaining deltas could be transferred with a simple rsync. - If you can find a way to make the snapshot commands store all further deltas around the time (just before/after) the migration in a separate delta file on a shared drive (NFS etc.), you could do that, then rsync all the (now stable) underlying files, then live migrate the running VM from using the shared delta and one hosts underlying files to using the same shared delta with the other hosts (identical) underlying files, then commit the snapshot delta from the NFS drive to the new host's copy of the next lower snapshot or base image. ASCII art illustration of the final tip above: +--------+ | VM | +--------+ / \ /4Migrate\ +---------+ +---------+ | Host1 | | Host2 | +---------+ +---------+ | \ / | | 2Snap \ /5Commit| | +----------+ | | | TempSnap | | On NFS etc. | +----------+ | | / \ | | / 3rsync \ | +---------+ +---------+ |Snapshots| |Snapshots| +---------+ +---------+ | 1copy | +---------+ +---------+ | Base | | Base | +---------+ +---------+ Note that disks are only identical during step 4 Enjoy Jakob -- Jakob Bohm, CIO, Partner, WiseMo A/S. http://www.wisemo.com Transformervej 29, 2860 Søborg, Denmark. Direct +45 31 13 16 10 This public discussion message is non-binding and may contain errors. WiseMo - Remote Service Management for PCs, Phones and Embedded |
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