On Thu, 2005-09-01 at 21:58 +0200, Jure Pečar wrote: > Hi all, > > Sorry if this is somewhat offtopic here ... > > Our telco is looking into linux HA solutions for their VoIP needs. Their > main requirement is that the failover happens in the order of a few 100ms. > > Can redhat cluster be tweaked to work reliably with such short time > periods? This would mean heartbeat on the level of few ms and status probes > on the level of 10ms. Is this even feasible? Possibly, I don't think it can do it right now. A couple of things to remember: * For such a fast requirement, you'll want a dedicated network for cluster traffic and a real-time kernel. * Also, "detection and initiation of recovery" is all the cluster software can do for you; your application - by itself - may take longer than this to recover. * It's practically impossible to guarantee completion of I/O fencing in this amount of time, so your application must be able to do without, or you need to create a new specialized fencing mechanism which is guaranteed to complete within a very fast time. * I *think* CMAN is currently at the whole-second granularity, so some changes would need to be made to give it finer granularity. This shouldn't be difficult (but I'll let the developers of CMAN answer this definitively, though... ;) ) * Clumanager 1.2.x (RHCS3) can theoretically operate at sub-second failure detection, but not at the levels you require (also, doing so is not tested nor supported anyway). -- Lon -- Linux-cluster@xxxxxxxxxx http://www.redhat.com/mailman/listinfo/linux-cluster
