AFAIK Cassandra will just pick the directory with the most space. Also AFAIK using multiple directories should only be considered a safety valve to fix problems such as the one you describe see http://www.mail-archive.com/user@cassandra.apache.org/msg07874.html
Aaron On 31 Mar 2011, at 15:14, Anurag Gujral wrote: > Hi All, > I had a single directory designated as data file directory in > cassandra ,but it ran out of space .I am adding a new data directory in > addition to the one I have .What should I do so that cassandra balance the > space on both of them. > > Thanks > Anurag