High latency at table level could be a result of no of factors. High tombstones GC Bloom filter fp I/O bottleneck Insufficient cache or threads
Since your partion size is not a problem here, try running major compaction on this table. Also you can turn on caching for this table. As mentioned above check other factors and eliminate one by one. Regards, Ashish On Sat 1 May, 2021, 06:41 vytenis silgalis, <vsilga...@gmail.com> wrote: > 17ms read latency for the 50th percentile is actually a pretty high > latency in my experience, I prefer to see the 75th percentile read latency > to be around 1-2ms. Of course it depends on your use case and what your > performance objectives are. > > On Thu, Apr 29, 2021 at 7:05 AM Kane Wilson <k...@raft.so> wrote: > >> It does imply the SSTables are being read - how big is your data size and >> how much memory on the nodes? It's certainly possible to get low latencies >> despite many SSTables, but I'd expect small read sizes paired with a lot of >> memory. >> >> >> raft.so - Cassandra consulting, support, managed services >> >> On Thu., 29 Apr. 2021, 08:44 Ayub M, <hia...@gmail.com> wrote: >> >>> The table has 24 sstables with size tiered compaction, when I run >>> nodetool tablehistograms I see 99% percentile of the queries are showing up >>> 24 as the number of sstables. But the read latency is very low, my >>> understanding from the tableshistograms's sstable column is - it shows how >>> many sstables were read to complete the query. If so reading 24 sstables >>> should take sometime, at least maybe couple of seconds. Am I missing >>> something here? Does checking against index/bloom filters count towards >>> sstable counter as well? >>> >>> Percentile SSTables Write Latency Read Latency Partition Size >>> Cell Count >>> (micros) (micros) (bytes) >>> 50% 24.00 17.08 17436.92 310 >>> 6 >>> 75% 24.00 24.60 20924.30 446 >>> 6 >>> 95% 24.00 42.51 62479.63 770 >>> 10 >>> 98% 24.00 51.01 74975.55 1597 >>> 17 >>> 99% 24.00 61.21 74975.55 3311 >>> 24 >>> Min 18.00 2.30 4866.32 87 >>> 0 >>> Max 24.00 943.13 89970.66 545791 >>> 17084 >>> >>>
