Re: [Xen-users] status of remus

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Sun, Apr 10, 2011 at 06:42:47PM -0400, Miles Fidelman wrote:
> Pasi Kärkkäinen wrote:
>> There's a new and active maintainer for Remus. He's been posting
>> many patches recently to xen-devel mailinglist.
>>    
>
> Good to hear!
>> Just remember Remus is FT (Fault Tolerance) solution..
>> often it's better use software/service based HA instead of vm-based FT.
>> FT is way slower than "normal" HA.
>>    
>
> Can you elaborate a bit, both re. what you see as the difference between  
> fault tolerance vs. HA, and re. speed?
>
> Currently, I'm running a collection of services on a single VM, with  
> DRBD/heartbeat/pacemaker failover to a 2nd node.  Failover takes a LONG  
> time.  Looks to me like Remus should provide instant failover.
>

Fault Tolerance means syncing the VM cpustate / memory / disk and net io 
between two physical hosts.. 

That is not very efficient and will create huge delays compared
to just executing the VM locally..

So you might get way better performance with running a active/active
HA cluster with a network/application level loadbalancer in front.

-- Pasi


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