Re:Dragonflydb – A modern replacement for Redis and Memcached
by baobob on Monday May 30, 2022 @07:03PM
(#31564561)
There is usually a tradeoff between latency and throughput, although I'm not so sure this would be true for your innovation, since you've eliminated a whole chunk of fixed overhead from the system (syscall batching). However, batching in general often implies added latency
If I recall ScyllaDB has some excellent examples of demonstrating this particular tradeoff visually. A simple option would be a scatter plot where X = latency, Y = load or similar, with points coloured according to the system under test. Probably there is a better option, but this would likely be enough to sell me at least
Re:Dragonflydb – A modern replacement for Redis and Memcached
by romange on Monday May 30, 2022 @07:13PM
(#31564614)
Well in that case, I hope to have an good answer for you. Right below the benchmark graph I deliberately put a table that shows 99th percentile lantencies at *peak* throughput as reported by memtier_benchmark.
99th latency percentile of Dragonfly at its peak throughput. I put it here as well
op r6g c6gn c7g
set 0.8ms 1ms 1ms
get 0.9ms 0.9ms 0.8ms
setex 0.9ms 1.1ms 1.3ms
Re:Dragonflydb – A modern replacement for Redis and Memcached
by lclarkmichalek on Tuesday May 31, 2022 @05:33AM
(#31567551)
There are also things that are unmitigated improvements.
Re:Dragonflydb – A modern replacement for Redis and Memcached
by pcthrowaway on Monday May 30, 2022 @05:55PM
(#31564049)
Does Dragonfly have a timeseries extension? Or does it support extensions?
The tradeoff the way I see it - one needs to implement 200 Redis commands from scratch. Besides, I think DF has a marginally higher 50th percentile latency. Say, if Redis has 0.3ms for 50th percentile, DF can have 0.4ms because it uses message passing for inter-thread communication. 99th percentiles are better in DF for the same throughput because DF uses more cpu power which reduces variance under load.
Re-durability - what durability is offerred by Redis? AOF ? We will provide similar durability guarantees with better performance than AOF. We already provide snapshotting that can be 30-50 faster than of Redis.