Re: reliable live migration of large and busy guests

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 06/11/12 23:41, Dan Magenheimer wrote:
>> From: Andrew Cooper [mailto:andrew.cooper3@citrix.com]
>> Sent: Tuesday, November 06, 2012 4:19 PM
>> To: xen-devel@lists.xen.org
>> Subject: Re: [Xen-devel] reliable live migration of large and busy guests
>>
>> As potential food for thought:
>>
>> Is there wisdom in having a new kind of live migrate which, when pausing
>> the VM on the source host, resumes the VM on the destination host.  Xen
>> would have to track not-yet-sent pages and pause the guest on pagefault,
>> and request the required page as a matter of priority.
>>
>> The advantages of this approach would be that a timing sensitive
>> workloads would be paused for far less time.  Even if it was frequently
>> being paused for pagefaults, the time to get a single page over the LAN
>> would be far quicker than the entire dirty set, at which point on
>> resume, the interrupt paths would fire again; The timing paths would
>> quickly become fully populated.  Further to that, a busy workload in the
>> guest dirtying a page which has already been sent will not result in any
>> further network traffic.
> Something like this?
>
> http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.184.2368 

Oh wow - something quite like that.  Thankyou very much.  I will read
the paper in full when I get a free moment, but the abstract looks very
interesting.

>From an idealistic point of view, it might be quite nice to have several
live migrate mechanisms, so the user can choose whether they value
minimum downtime, minimum network utilisation, or maximum safety.

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com