Hi Michael, I have had similar problems in the past, and found this Last Pickle post very useful: https://thelastpickle.com/blog/2016/12/08/TWCS-part1.html
This should help you pinpoint what is stopping the SSTables being deleted. Assuming you are never manually deleting records from the table then there is no need to have a large gc_grace_seconds, as a large one is there to ensure tombstones are replicated correctly, and you won’t have any tombstones to worry about. If you are doing manual deletes, then that could be the cause of the issue, I wrote a post here about why that would be an issue: http://www.redshots.com/cassandra-twcs-must-have-ttls/ After reading these if you are still having problems please let us know. Thanks Paul > On 6 Oct 2021, at 09:42, Michel Barret <michel.bar...@inovatel.com> wrote: > > Hello, > > I try to use cassandra (3.11.5) with 8 nodes (in single datacenter). I use > one simple table, all data are inserted with 31 days TTL (the data are never > updated). > > I use the TWCS strategy with: > - 'compaction_window_size': '24' > - 'compaction_window_unit': 'HOURS' > - 'max_threshold': '32' > - 'min_threshold': '4' > > Each node run one time by week a 'nodetool repair' and our gc_grace_seconds > is set to 10 days. > > I track the storage of nodes and the partition used for cassandra data (only > use for this) is consuming to ~40% after one month. > > But cassandra consume continuously more space, if I read the sstables with > sstabledump I find very old tombstones like it : > > "liveness_info" : { "tstamp" : "2021-07-26T08:15:00.092897Z", "ttl" : > 2678400, "expires_at" : "2021-08-26T08:15:00Z", "expired" : true } > > I don't understand why this tombstone isn't erased. I believe that I apply > all I found on internet without improvement. > > Anybody had a clue to fix my problem? > > Have a nice day
