How does minor compaction is triggered? Is it triggered Only when a new SStable is added?
I was wondering if triggering a compaction with minimumCompactionThreshold set to 1 would be useful. If this can happen I assume it will do compaction on files with similar size and remove deleted rows on the rest. Shimi On Tue, Jan 4, 2011 at 9:56 PM, Peter Schuller <peter.schul...@infidyne.com>wrote: > > I don't have a problem with disk space. I have a problem with the data > > size. > > [snip] > > > Bottom line is that I want to reduce the number of requests that goes to > > disk. Since there is enough data that is no longer valid I can do it by > > reclaiming the space. The only way to do it is by running Major > compaction. > > I can wait and let Cassandra do it for me but then the data size will get > > even bigger and the response time will be worst. I can do it manually but > I > > prefer it to happen in the background with less impact on the system > > Ok - that makes perfect sense then. Sorry for misunderstanding :) > > So essentially, for workloads that are teetering on the edge of cache > warmness and is subject to significant overwrites or removals, it may > be beneficial to perform much more aggressive background compaction > even though it might waste lots of CPU, to keep the in-memory working > set down. > > There was talk (I think in the compaction redesign ticket) about > potentially improving the use of bloom filters such that obsolete data > in sstables could be eliminated from the read set without > necessitating actual compaction; that might help address cases like > these too. > > I don't think there's a pre-existing silver bullet in a current > release; you probably have to live with the need for > greater-than-theoretically-optimal memory requirements to keep the > working set in memory. > > -- > / Peter Schuller >
