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Subject [GitHub] ratcashdev edited a comment on issue #1334: Experimental settings to achieve 5 ms latency
Date Mon, 30 Jul 2018 06:02:56 GMT
ratcashdev edited a comment on issue #1334: Experimental settings to achieve 5 ms latency
URL: https://github.com/apache/incubator-pulsar/issues/1334#issuecomment-408586469
 
 
   Thank you for the detailed explanation, @sijie.
   So if I understand all of that correctly, 
   1. when we compare the two in their default configuration (default config being the `apple`),
Kafka will probably have lower latency than Pulsar for publishing, since - at least up until
know - it could not control fsync behavior. Users need to keep in mind the difference in behaviour
at their default settings:  `filesystem-persistence` (Kafka) vs `direct-to-disk-persistence`
and forced fsync (Pulsar)
   2. when we compare the two in a config that's comparable in behavior (here identical behavior
being the `apple`), Kafka (with some extra settings getting it closer to `direct-to-disk-persistence`)
will likely provide higher latency compared to Pulsar (with its default setting in this regard).
   3. Pulsar using `filesystem-persistence` was not possible up until recently (can you please
pinpoint the exact config that needs to be tweaked?) , and it's likely that it will provide
lower latencies, but not lower than with a `non-persistent` topic, will it?
   
   And yet back to option No 2 above: Kafka , by default, (first?) replicates the data, then
writes to the filesystem. What's the order for Pulsar, when we disable forced fsync (and also
when its on)?

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