Hello, It's a very common but somewhat complex topic. We wrote about it 2 years ago and I really think this post might have answers you are looking for: http://thelastpickle.com/blog/2016/07/27/about-deletes-and-tombstones.html
Something that you could try (if you do care ending up with one big sstable :)) is to enable 'unchecked_tombstone_compaction'. This removes a pre-check supposed to only trigger tombstone compactions when it is worth it (ie there is no sstable overlaps) but that over time proved to be inefficient from a tombstone eviction perspective. If data can actually be deleted (no overlaps, gc_grace_seconds lowered or reached, ...) then changing option 'unchecked_tombstone_compaction' to 'true' might do a lot of good in terms of disk space. Be aware that a bunch of compactions might be triggered and that disk space will start by increasing before (possibly) reducing after the compactions. The gc_grace of table was default (10 days), now i set that to 0, although > many compactions finished but no space reclaimed so far. > Be aware that if some deletes did not reach all the replicas, the data will eventually come back as lowering the gc_grace_seconds, you don't allow repairs to process the data before tombstones are actually evicted. Also, by setting the gc_grace_seconds to 0, you also disabled the hints altogether. gc_grace_seconds should always be equivalent to 'max_hint_windows_in_ms'. My colleague Radovan wrote a post with more information on this: http://thelastpickle.com/blog/2018/03/21/hinted-handoff-gc-grace-demystified.html Good luck with your tombstones, again, those are a bit tricky to handle sometimes ;-) C*heers, ----------------------- Alain Rodriguez - @arodream - al...@thelastpickle.com France / Spain The Last Pickle - Apache Cassandra Consulting http://www.thelastpickle.com 2018-05-31 16:19 GMT+01:00 Nicolas Guyomar <nicolas.guyo...@gmail.com>: > Hi, > > You need to manually force compaction if you do not care ending up with > one big sstable (nodetool compact) > > On 31 May 2018 at 11:07, onmstester onmstester <onmstes...@zoho.com> > wrote: > >> Hi, >> I've deleted 50% of my data row by row now disk usage of cassandra data >> is more than 80%. >> The gc_grace of table was default (10 days), now i set that to 0, >> although many compactions finished but no space reclaimed so far. >> How could i force deletion of tombstones in sstables and reclaim the disk >> used by deleted rows? >> I'm using cassandra on a single node. >> >> Sent using Zoho Mail <https://www.zoho.com/mail/> >> >> >> >
