Sub columns for a super column do serialise their time stamp, they are just the same as regular column. The super column does not have a timestamp of it's own. It does have it's own tombstone marker though.
Super Column does not take a huge amount more disk space, just the name a shot int, two ints and a long int. Some things to consider: - were their any compacted files on disk ? these are sstables that have one zero length file with COMPACTED in the name. These files will be deleted at some point. - What did the commit log directory look like ? Flushing should have check pointed all the log segments and deleted the log files. - I'm assuming this was a single node, if not was the node collecting Hinted - Did the standard CF have cache saving enabled ? Take a poke around the /var/lib/cassandra tree and let us know if you see anything interesting. Cheers ----------------- Aaron Morton Freelance Cassandra Developer @aaronmorton http://www.thelastpickle.com On 14 May 2011, at 03:15, Alexis RodrÃguez wrote: > cassandra-people, > > I'm trying to measure disk usage by cassandra after inserting some columns in > order to plan disk sizes and configurations for future deploys. > > My approach is very straightforward: > > clean_data (stop_cassandra && rm -rf > /var/lib/cassandra/{dara,commitlog,saved_caches}/*) > perform_inserts > measure_disk_usage (nodetool -flush && du -ch /var/lib/cassandra) > > There are two types of inserts: > In a simple column with key, name and value a random string of size 100 > In a super-column with key, super-column-name, name and value a random string > of size 100 > But surprisingly when I'm inserting 100 million columns on a simple column it > uses more disk than the same amount in a super-column. How can that be > possible? > > For simple column 41984 MB and for super-column 29696, the difference is more > than noticeable! > > Somebody told me yesterday that super-columns don't have a per-column > timestamp, but... it in my case, even if every data was in the same > super-column-key it will not explain the difference! > > > ps: sorry, English is not my first language > > > <results.eps>
