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 >> >>
