On 3/12/12 7:13 PM, Pedro Ruivo wrote: > On 3/10/12 5:07 PM, Bela Ban wrote: >> If so, then I can assume that a transactional modification touching a >> number of keys will almost always touch *all* nodes ? Example: >> - We have 10 nodes >> - numOwners = 2 >> - If we have a good consistent hash, I can assume that I have to modifiy >> 5 different keys (10 / 2) on average in a TX to touch *all* nodes in the >> cluster with the PREPARE/COMMIT phase, correct ? >> >> If my last statement is correct, is it safe to assume that with DIST and >> transactional modifications, I will have a lot of TX contention / >> collisions ? > > We have run experiments with ISPN 5.2 and TPC-C (1 warehouse, which > gives a high probability of contention among transactions), and compared > it with ISPN 5.0 (where locks were acquired on all replicas of a key, > not only on the primary). > > The results running w/o write skew check and 10 nodes on our cluster > (number of owners=2) follow: > > Tx/sec Abort Rate > 5.2 12 15 > 5.0 3 30 > 5.0-TOM 60 0
Excellent ! It shows that 2PC has really improved between 5.0 and 5.2... Have you run TOM on Infinispan-5.2 / JGroups 3.1 yet ? It should theoretically still be 60 TXs/sec. But even compared to 12, this is still much better ! >> Also, if we touch almost all nodes, would it make sense to use SEQUENCER >> for >> *all* updates ? Would this obviliate the need for TOM (total order for >> partial replication) ? > This could be done, you are right, it's what sometimes is called > "non-genuine" partial replication. Our take on this is that this will > work good on small scale clusters, not on large ones. I agree -- Bela Ban, JGroups lead (http://www.jgroups.org) _______________________________________________ infinispan-dev mailing list [email protected] https://lists.jboss.org/mailman/listinfo/infinispan-dev
