Sergio, if you’re looking for a new frequency for your repairs because of the change, if you are using reaper, then I’d go for repair_freq <= gc_grace / 2.
Just serendipity with a conversation I was having at work this morning. When you actually watch the reaper logs then you can see situations where unlucky timing with skipped nodes can make the time to remove a tombstone be up to 2 x repair_run_time. If you aren’t using reaper, your mileage will vary, particularly if your repairs are consistent in the ordering across nodes. Reaper can be moderately non-deterministic hence the need to be sure you can complete at least two repair runs. R From: Sergio <lapostadiser...@gmail.com> Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org> Date: Tuesday, January 21, 2020 at 7:13 PM To: "user@cassandra.apache.org" <user@cassandra.apache.org> Subject: Re: Is there any concern about increasing gc_grace_seconds from 5 days to 8 days? Message from External Sender Thank you very much for your response. The considerations mentioned are the ones that I was expecting. I believe that I am good to go. I just wanted to make sure that there was no need to run any other extra command beside that one. Best, Sergio On Tue, Jan 21, 2020, 3:55 PM Jeff Jirsa <jji...@gmail.com<mailto:jji...@gmail.com>> wrote: Note that if you're actually running repairs within 5 days, and you adjust this to 8, you may stream a bunch of tombstones across in that 5-8 day window, which can increase disk usage / compaction (because as you pass 5 days, one replica may gc away the tombstones, the others may not because the tombstones shadow data, so you'll re-stream the tombstone to the other replicas) On Tue, Jan 21, 2020 at 3:28 PM Elliott Sims <elli...@backblaze.com<mailto:elli...@backblaze.com>> wrote: In addition to extra space, queries can potentially be more expensive because more dead rows and tombstones will need to be scanned. How much of a difference this makes will depend drastically on the schema and access pattern, but I wouldn't expect going from 5 days to 8 to be very noticeable. On Tue, Jan 21, 2020 at 2:14 PM Sergio <lapostadiser...@gmail.com<mailto:lapostadiser...@gmail.com>> wrote: https://stackoverflow.com/a/22030790<https://urldefense.proofpoint.com/v2/url?u=https-3A__stackoverflow.com_a_22030790&d=DwMFaQ&c=9Hv6XPedRSA-5PSECC38X80c1h60_XWA4z1k_R1pROA&r=OIgB3poYhzp3_A7WgD7iBCnsJaYmspOa2okNpf6uqWc&m=qt1NAYTks84VVQ4WGXWkK6pw85m3FcuUjPRJPdIHMdw&s=aEgz5F5HRxPT3w4hpfNXQRhcchwRjrpf7KB3QyywO_Q&e=> For CQLSH alter table <table_name> with GC_GRACE_SECONDS = <seconds>; Il giorno mar 21 gen 2020 alle ore 13:12 Sergio <lapostadiser...@gmail.com<mailto:lapostadiser...@gmail.com>> ha scritto: Hi guys! I just wanted to confirm with you before doing such an operation. I expect to increase the space but nothing more than this. I need to perform just : UPDATE COLUMN FAMILY cf with GC_GRACE = 691,200; //8 days Is it correct? Thanks, Sergio
