Re: [infinispan-dev] Let me understand DIST

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

> 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.