Apart from the compaction, you might want to also look at free space required for repairs. This could be problem if you have large rows as repair is not at column level.
> On Nov 28, 2013, at 19:21, Robert Wille <rwi...@fold3.com> wrote: > > I’m trying to estimate our disk space requirements and I’m wondering about > disk space required for compaction. > > My application mostly inserts new data and performs updates to existing data > very infrequently, so there will be very few bytes removed by compaction. It > seems that if a major compaction occurs, that performing the compaction will > require as much disk space as is currently consumed by the table. > > So here’s my question. If Cassandra only compacts one table at a time, then I > should be safe if I keep as much free space as there is data in the largest > table. If Cassandra can compact multiple tables simultaneously, then it seems > that I need as much free space as all the tables put together, which means no > more than 50% utilization. So, how much free space do I need? Any rules of > thumb anyone can offer? > > Also, what happens if a node gets low on disk space and there isn’t enough > available for compaction? If I add new nodes to reduce the amount of data on > each node, I assume the space won’t be reclaimed until a compaction event > occurs. Is there a way to salvage a node that gets into a state where it > cannot compact its tables? > > Thanks > > Robert >
