Re: KVM in HA active/active + fault-tolerant configuration

[g.danti@assyoma.it]

On 2013-08-21 21:40, Brian Jackson wrote:
> On Wednesday, August 21, 2013 6:02:31 AM CDT, g.danti@assyoma.it 
> wrote:
>> Hi all,
>> I have a question about Linux KVM HA cluster.
>> 
>> I understand that in a HA setup I can live migrate virtual machine 
>> between host that shares the same storage (via various methods, eg: 
>> DRDB). This enable us to migrate the VMs based on hosts loads and 
>> performance.
>> 
>> ìMy current understanding is that, with this setup, an host crash 
>> will cause the VMs to be restarded on another host.
>> 
>> However, I wonder if there is a method to have a fully fault-tolerant 
>> HA configuration, where for "fully fault-tolerant" I means that an 
>> host crash (eg: power failures) will cause the VMs to be migrated to 
>> another hosts with no state change. In other word: it is possible to 
>> have an always-synchronized (both disk & memory) VM instance on 
>> another host, so that the migrated VM does not need to be restarted 
>> but only restored/unpaused? For disk data synchronization we can use 
>> shared storages (bypassing the problem) or something similar do DRDB, 
>> but what about memory?
> 
> 
> You're looking for something that doesn't exist for KVM. There was a
> project once for it called Kemari, but afaik, it's been abandoned for
> a while.

Hi Brian,
thank you for your reply.

As I googled extensively without finding anything, I was prepared to a 
similar response.

Anyway, from what I understand, Qemu already use a similar approach 
(tracking dirty memory pages) when live migrating virtual machines to 
another host.

So what is missing is the "glue code" between Qemu and KVM/libvirt 
stack, right?

Thanks again.

> 
> 
>> 
>> Thank you,
>> regards.
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