[CASSANDRA-8371] DateTieredCompactionStrategy is always compacting

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Duplicate
• Labels: compaction dtcs performance
• Severity: Normal
• Since Version: 2.0.11
• Assignee: Björn Hegerfors
• Reporter: Michael Semb Wever

Authors

Björn Hegerfors

• Created: 24/Nov/14 21:28
• Updated: 04/Oct/19 16:20
• Resolved: 07/Sep/15 16:26

Description

Running 2.0.11 and having switched a table to DTCS we've seen that disk IO and gc count increase, along with the number of reads happening in the "compaction" hump of cfhistograms.

Data, and generally performance, looks good, but compactions are always happening, and pending compactions are building up.

The schema for this is

CREATE TABLE search (
  loginid text,
  searchid timeuuid,
  description text,
  searchkey text,
  searchurl text,
  PRIMARY KEY ((loginid), searchid)
);

We're sitting on about 82G (per replica) across 6 nodes in 4 DCs.
CQL executed against this keyspace, and traffic patterns, can be seen in slides 7+8 of https://prezi.com/b9-aj6p2esft/

Attached are sstables-per-read and read-latency graphs from cfhistograms, and screenshots of our munin graphs as we have gone from STCS, to LCS (week ~44), to DTCS (week ~46).

These screenshots are also found in the prezi on slides 9-11.

pmcfadin, Bj0rn,

Can this be a consequence of occasional deleted rows, as is described under (3) in the description of CASSANDRA-6602 ?

Issue Links

• duplicates: CASSANDRA-9644 DTCS configuration proposals for handling consequences of repairs