Github user roshannaik commented on the issue: https://github.com/apache/storm/pull/2270 Ok thats great since I noticed that the -c mode was not working for the grouping option due a bug in the topo creation code . BTW... I noticed that I incorrectly said something important earlier that I want to correct... actually the ACKer is slower than the inter-worker (and not the other way around as I accidentally said). Your observations about LoadAware are similar to mine ... which i discovered when doing STORM-2306. With STORM-2306, both ACKer and inter-worker throughputs are a good deal higher (but nowhere close to where they really should be).. So I felt it would be interesting to run this analysis on it to observe impact. Since this patch doesn't apply easily on 2306, it took me a bunch of time to manually resolve it. Anyway here are the results: **No ACK mode** LocalOrShuffle: ~**7.12 mill/sec** LASG : ~ **6.5 mill /sec** **ACK mode** LocalOrShuffle: ~ **1.23 mill/sec** . Latency: avg: **0.013 ms** max: **0.015 ms** LASG : ~ **1.26 mill/sec** Latency: avg: **0.017 ms** max: **0.035 ms** 8% slower in noACK mode. Avg latency is close, max latency is 2x+ higher in ACK mode. But should be ok. Overall these numbers look acceptable to me. Once (hopefully soon) we fix the two bottlenecks (ACKer & interworker), there is a possibility that we may have to revisit and optimize this. Have you had a chance to test this on a real multi-rack cluster and make any observations ?
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