From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42145) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YHHwz-0003CF-0W for qemu-devel@nongnu.org; Fri, 30 Jan 2015 15:13:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YHHwt-00074E-Ui for qemu-devel@nongnu.org; Fri, 30 Jan 2015 15:13:56 -0500 Received: from mail-we0-x230.google.com ([2a00:1450:400c:c03::230]:39999) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YHHwt-000748-KA for qemu-devel@nongnu.org; Fri, 30 Jan 2015 15:13:51 -0500 Received: by mail-we0-f176.google.com with SMTP id w62so29080023wes.7 for ; Fri, 30 Jan 2015 12:13:50 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <54CBD9C8.2040909@redhat.com> References: <54CBD9C8.2040909@redhat.com> Date: Fri, 30 Jan 2015 14:13:50 -0600 Message-ID: From: Yaodong Yang Content-Type: multipart/alternative; boundary=047d7ba96ed833fcdb050de43e43 Subject: Re: [Qemu-devel] vm live storage migration approach. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: qemu-devel@nongnu.org --047d7ba96ed833fcdb050de43e43 Content-Type: text/plain; charset=UTF-8 An follow up questions. Suppose I have a running VM with two virtual disks, I would like to migrate the vm from host A to host B. Both host A and host B have their own isolated storage devices. Is there anyway to migrate the vm's memory, two virtual disk images and other states together from host A to host B? Can drive_mirror command itself finish this job? I noticed that drive_mirror only mirror for one virtual disk and require both the source and destination share the same storage namespace. I do not know how to migrate the whole VM (memory, storage, network ) together from host A to host B, given that host A and host B have NO shared storage resource. Could you show me an example, if possible? I know "migrate -b" works well for this purpose. But the downside is "migrate -b" does not mirror Write Requests to both host A and host B during migration. In this case, "migrate -b" has a higher VM downtime during the migration. Yaodong On Fri, Jan 30, 2015 at 1:21 PM, Eric Blake wrote: > On 01/30/2015 09:25 AM, Yaodong Yang wrote: > > Hi all, > > > > I'm investigating the current schemes for the VM live storage migration > in > > QEMU system. I have the following questions: > > > > 1. What is the functionality of drive_mirror in QEMU? Is it designed as a > > VM live storage migration approach? > > Yes. drive-mirror was added precisely to support live storage migration. > > > > > 2. What's the difference between drive_mirror and vMotion? I learned that > > vMotion employs IO Mirroring mechanism to migration a running VM with all > > the virtual disk images. Are there any other mechanisms inside QEMU serve > > this purpose as well? > > vMotion is not part of qemu, so I'm not sure what it does. Therefore, I > cannot make a fair comparison. > > > > > I'm looking for a mechanism in QEMU, which is similar to vMotion ( IO > > Mirroring) in ESX environment. > > Look at drive-mirror, block-backup, quorum drives, and lots of recent > threads on this list about adding redundant processing (such as the term > "COLO") for how to piece together lower-level blocks into whatever drive > mirroring scheme you can think of. > > > -- > Eric Blake eblake redhat com +1-919-301-3266 > Libvirt virtualization library http://libvirt.org > > -- Yaodong Yang yaodong.yangy@gmail.com or yyang@cse.unl.edu Computer Science and Engineering Department University of Nebraska-Lincoln Lincoln, NE, USA --047d7ba96ed833fcdb050de43e43 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
An follow up questions.

Suppose I have = a running VM with two virtual disks, I would like to migrate the vm from ho= st A to host B. Both host A and host B have their own isolated storage devi= ces. Is there anyway to migrate the vm's memory, two virtual disk image= s and other states together from host A to host B? Can drive_mirror command= itself finish this job? I noticed that drive_mirror only mirror for one vi= rtual disk and require both the source and destination share the same stora= ge namespace. I do not know how to migrate the whole VM (memory, storage, n= etwork ) together from host A to host B, given that host A and host B have = NO shared storage resource.

Could you show me an e= xample, if possible?

I know "migrate -b"= works well for this purpose. But the downside is "migrate -b" do= es not mirror Write Requests to both host A and host B during migration. In= this case, "migrate -b" has a higher VM downtime during the migr= ation.

Yaodong

On Fri, Jan 30, 2015 at 1:21 PM, Eric Bla= ke <eblake@redhat.com> wrote:
On 01/30/2015 09:25 AM, Yaodong Yang wrote:
> Hi all,
>
> I'm investigating the current schemes for the VM live storage migr= ation in
> QEMU system. I have the following questions:
>
> 1. What is the functionality of drive_mirror in QEMU? Is it designed a= s a
> VM live storage migration approach?

Yes. drive-mirror was added precisely to support live storage migrat= ion.

>
> 2. What's the difference between drive_mirror and vMotion? I learn= ed that
> vMotion employs IO Mirroring mechanism to migration a running VM with = all
> the virtual disk images. Are there any other mechanisms inside QEMU se= rve
> this purpose as well?

vMotion is not part of qemu, so I'm not sure what it does.=C2=A0= Therefore, I
cannot make a fair comparison.

>
> I'm looking for a mechanism in QEMU, which is similar to vMotion (= IO
> Mirroring) in ESX environment.

Look at drive-mirror, block-backup, quorum drives, and lots of recen= t
threads on this list about adding redundant processing (such as the term "COLO") for how to piece together lower-level blocks into whateve= r drive
mirroring scheme you can think of.


--
Eric Blake=C2=A0 =C2=A0eblake redhat com=C2=A0 =C2=A0 +1-919-301-3266
Libvirt virtualization library http://libvirt.org




--
Yaod= ong Yang
Computer Science and Engineering Depa= rtment
University of Nebraska-Lincoln
Lincoln, NE, USA
--047d7ba96ed833fcdb050de43e43--