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Re: [Xen-API] Storage XenMotion - Just sync


  • To: xen-api@xxxxxxxxxxxxx
  • From: Alexandre Kouznetsov <alk@xxxxxxxxxx>
  • Date: Wed, 09 Jan 2013 19:18:42 -0600
  • Delivery-date: Thu, 10 Jan 2013 01:18:54 +0000
  • List-id: User and development list for XCP and XAPI <xen-api.lists.xen.org>

Hello.

El 09/01/13 16:27, Chris Dutton escribió:
Hello,

What I am trying to accomplish is keep a vm on one host (a) in sync with
another vm on host (b). They are both using local storage for the SR,
which led me to investigate SXM. But it looks like it does just a little
more then I want.

 From the Storage XenMotion wiki page:

Each of a VM’s disks are snapshotted, and from the point of the snapshot
onwards, all of the disk’s writes are synchronously mirrored to the
destination storage repository. In the background, the snapshotted disk
is copied to the destination location. Once a snapshot has finished
copying, the next disk to be migrated is snapshot/mirrored.

What I am hoping to do is everything except the last step (the actual
migration).

Since you are not actually migrating the VM, maybe the sync is unnecessary (it might became obsolete in matter of seconds), but a copy of a snapshot.

Maybe this reference would help:
http://lists.xen.org/archives/html/xen-api/2013-01/msg00038.html
(and the rest of the thread, about vm-migrate behavior)

Note that the reference is about offline migration, but the mechanics is similar. In your case, you would probably want to do a snapshot of the VDI being used, and copy that snapshot to the other host, then attach it to the target VM.


The sync does not necessarily have to be synchronous for my situation,
so maybe run a sync as a cron job but when a sync happens I only want
the deltas copied (not a full snapshot).
As I understand it, yhe method I suggested will not allow you to update the copy of the snapshot. Only create a new copy.


--
Alexandre Kouznetsov


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