Memtable Data Size is the number of bytes you Column Family is taking up. Have you read the section on "Repairing missing or inconsistent data" here http://wiki.apache.org/cassandra/Operations . It describes the nodetool repair operation used to repair inconsistent data.
Aaron On 28 Oct 2010, at 22:35, Utku Can Topçu wrote: > Gary, Thank you for your comments. > > I also have another question in mind: > - If in all nodes "nodetool cfstats" shows that the memtable size is 0. Then > can I be sure that it's safe to assume that all values are consistent? > > Regards, > Utku > > On Wed, Oct 27, 2010 at 3:24 PM, Gary Dusbabek <gdusba...@gmail.com> wrote: > On Wed, Oct 27, 2010 at 05:08, Utku Can Topçu <u...@topcu.gen.tr> wrote: > > Hi, > > > > For a columnfamily in a keyspace which has RF=3, I'm issuing writes with > > ConsistencyLevel.ONE. > > > > in the configuration I have: > > - memtable_flush_after_mins : 30 > > - memtable_throughput_in_mb : 32 > > > > I'm writing to this columnfamily continuously for about 1 hour then stop > > writing. > > > > So the question is: > > > > How long should I wait after stopping writes to that particular CF so that > > all writes take place and data contained in the CF will be consistent. > > There is no way to determine this precisely. Depending on your nodes > and network it could be as short as a few milliseconds or much longer. > > > Which metrics should I be checking to ensure that the CF is now consistent? > > Execute a read using ConsistencyLevel.ALL. If the value is not yet > consistent, read repair will ensure that it soon will be. Another > approach is to write using ConsistencyLevel.ALL, although that would > decrease your write throughput. > > > > > And additionally if I was using ConsistencyLevel.QUORUM or > > ConsistencyLevel.ALL would it make a difference? > > Precisely. > > > Would reducing the RF=3 to RF=1 would it make my life on this decision > > easier? > > It would make determining consistency better, but RF=1 isn't going to > be very fault tolerant. > > Gary. >
