> I have a Cassandra installation where we plan to store 1Tb of data, split > between two 1Tb disks. In general it's a good idea to limit the per node storage to 300GB to 400GB. This has more to do with operational issues that any particular issue with cassandra. However storing a very large number of keys on a single node can result in high memory usage while the server is idling, and reduced read performance. > I know that tiered compaction needs 50% free disk space for worst case > situation. Not really now days, but it's a good idea to treat 50% as a soft limit.
> How does this combine with the disk split? Whenever a new file is written to disk it will use the data directory with the most space. In general we recommend using a single data directory. Hope that helps. ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 21/06/2012, at 10:56 PM, Flavio Baronti wrote: > Hi, > > I have a Cassandra installation where we plan to store 1Tb of data, split > between two 1Tb disks. > Tiered compation should be better suited for our workload (append-only, > deletion of old data, few reads). > I know that tiered compaction needs 50% free disk space for worst case > situation. How does this combine with the disk split? What happens if I have > 500Gb of data in one disk and 500Gb in the other? Won't compaction try to > build a single 1Tb file, failing since there are only 500Gb free on each disk? > > Flavio >
