Alex, a single (largish) SSTable or any other SSTable for a table, which does not get any writes (with e.g. deletes) anymore, will most likely not be part of an automatic minor compaction anymore, thus may stay forever on disk, if I don’t miss anything crucial here. Might be different though, if you are entirely writing TTL-based, cause single SSTable based automatic tombstone compaction may kick in here, but I’m not really experienced with that.
We had been suffering a lot with storing timeseries data with STCS and disk capacity to have the cluster working smoothly and automatic minor compactions kicking out aged timeseries data according to our retention policies in the business logic. TWCS is unfortunately not an option for us. So, we did run major compactions every X weeks to reclaim disk space, thus from an operational perspective, by far not nice. Thus, finally decided to change STCS min_threshold from default 4 to 2, to let minor compactions kick in more frequently. We can live with the additional IO/CPU this is causing, thus is our current approach to disk space and sizing issues we had in the past. Thomas From: Oleksandr Shulgin <oleksandr.shul...@zalando.de> Sent: Dienstag, 11. September 2018 09:47 To: User <user@cassandra.apache.org> Subject: Re: Drop TTLd rows: upgradesstables -a or scrub? On Tue, Sep 11, 2018 at 9:31 AM Steinmaurer, Thomas <thomas.steinmau...@dynatrace.com<mailto:thomas.steinmau...@dynatrace.com>> wrote: As far as I remember, in newer Cassandra versions, with STCS, nodetool compact offers a ‘-s’ command-line option to split the output into files with 50%, 25% … in size, thus in this case, not a single largish SSTable anymore. By default, without -s, it is a single SSTable though. Thanks Thomas, I've also spotted the option while testing this approach. I understand that doing major compactions is generally not recommended, but do you see any real drawback of having a single SSTable file in case we stopped writing new data to the table? -- Alex The contents of this e-mail are intended for the named addressee only. It contains information that may be confidential. Unless you are the named addressee or an authorized designee, you may not copy or use it, or disclose it to anyone else. If you received it in error please notify us immediately and then destroy it. Dynatrace Austria GmbH (registration number FN 91482h) is a company registered in Linz whose registered office is at 4040 Linz, Austria, Freistädterstraße 313
