On Wed, May 15, 2013 at 1:27 AM, Alain RODRIGUEZ <arodr...@gmail.com> wrote: > Rob, I was wondering something. Are you a commiter working on improving the > repair or something similar ?
I am not a committer [1], but I have an active interest in potential improvements to the best practices for repair. The specific change that I am considering is a modification to the default gc_grace_seconds value, which seems picked out of a hat at 10 days. My view is that the current implementation of repair has such negative performance consequences that I do not believe that holding onto tombstones for longer than 10 days could possibly be as bad as the fixed cost of running repair once every 10 days. I believe that this value is too low for a default (it also does not map cleanly to the work week!) and likely should be increased to 14, 21 or 28 days. > Anyway, if a commiter (or any other expert) could give us some feedback on > our comments (Are we doing well or not, whether things we observe are normal > or unexplained, what is going to be improved in the future about repair...) 1) you are doing things according to best practice 2) unfortunately your experience with significantly degraded performance, including a blocked go-live due to repair bloat is pretty typical 3) the things you are experiencing are part of the current implementation of repair and are also typical, however I do not believe they are fully "explained" [2] 4) as has been mentioned further down thread, there are discussions regarding (and some already committed) improvements to both the current repair paradigm and an evolution to a new paradigm Thanks to all for the responses so far, please keep them coming! :D =Rob [1] hence the (unofficial) tag for this thread. I do have minor patches accepted to the codebase, but always merged by an actual committer. :) [2] driftx@#cassandra feels that these things are explained/understood by core team, and points to https://issues.apache.org/jira/browse/CASSANDRA-5280 as a useful approach to minimize same.
