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The "MemtableSSTable" page has been changed by JonathanEllis. http://wiki.apache.org/cassandra/MemtableSSTable?action=diff&rev1=16&rev2=17 -------------------------------------------------- Since the input SSTables are all sorted by key, merging can be done efficiently, still requiring no random i/o. Once compaction is finished, the old SSTable files may be deleted: note that in the worst case (a workload consisting of no overwrites or deletes) this will temporarily require 2x your existing on-disk space used. In today's world of multi-TB disks this is usually not a problem but it is good to keep in mind when you are setting alert thresholds. - SSTables that are obsoleted by a compaction are deleted asynchronously when the JVM performs a GC. You can force a GC from jconsole if necessary, but Cassandra will force one itself if it detects that it is low on space. A compaction marker is also added to obsolete sstables so they can be deleted on startup if the server does not perform a GC before being restarted. + SSTables that are obsoleted by a compaction are deleted asynchronously when the JVM performs a GC. If a GC does not occur before Cassandra is shut down, Cassandra will remove them when it restarts. You can force a GC from jconsole if necessary, but Cassandra will force one itself if it detects that it is low on space. A compaction marker is also added to obsolete sstables so they can be deleted on startup if the server does not perform a GC before being restarted. ColumnFamilyStoreMBean exposes sstable space used as getLiveDiskSpaceUsed (only includes size of non-obsolete files) and getTotalDiskSpaceUsed (includes everything).
