On Fri, Nov 13, 2009 at 12:20 AM, TuxRacer69 <[email protected]> wrote: > Hello Cassandra Users! > > On the wiki page: > http://wiki.apache.org/cassandra/ArticlesAndPresentations > there is a link to J. Ellis pdf: > http://assets.en.oreilly.com/1/event/27/Cassandra_%20Open%20Source%20Bigtable%20+%20Dynamo%20Presentation.pdf > > > At page 41 we have: (Roadmap) Cassandra 0.5 > Cassandra 0.5 > Millions of columns per row > This will require another data format change > > Question 1: > ----------------- > Is there any Jira logged for this change yet? > I'd like to understand > a) if a full data rebuild will be necessary for upgrading from 0.4.X to 0.5 > b) what the limitations currently are in Cassandra. > - How many keys per column family > - How many columns per key in a standard column family > - How many columns per key in a super column family, and how many subcolumns > within a supercolumn key > > Page http://wiki.apache.org/cassandra/CassandraLimitations > says "The main limitation on column and supercolumn size is that all data > for a single key and column must fit (on disk) on a single machine in the > cluster." but that does not really answer the questions above (as know we > can have 1Tb disk cheaply) > > Question 2: > ---------------- > Page 15 and 16: Architecture layer. > How could we defined Memtables and SStables? What the two 'S' stand for in > SSTable?
A Memtable is Cassandra's in-memory representation of key/value pairs before the data gets flushed to disk as an SSTable. An SSTable (terminology borrowed from Google) stands for Sorted Strings Table and is a file of key/value string pairs, sorted by keys. Edmond > > Thanks a lot > Alex > > >
