Since this thread has now gone on for a while... As far as I can tell you never specify the characteristics of your writes. Evaluating expected write throughput in terms of "MB/s to disk" is pretty impossible if one does not know anything about the nature of the writes. If you're expecting 50 MB, is that reasonable? I don't know; if you're writing a gazillion one-byte values with shortish keys, 50 MB/seconds translates to a *huge* amounts of writes per second and you're likely to be CPU bound even in the most efficient implementation reasonably possible.
If on the other hand you're writing large values (say slabs of 128k) you might more reasonably be expecting higher disk throughput. I don't have enough hands-on experience with cassandra to have a feel for the CPU vs. disk in terms of bottlenecking, and when we expect to bottleneck on what, but I can say that it's definitely going to matter quite a lot what *kind* of writes you're doing. This tends to be the case regardless of the database system. -- / Peter Schuller aka scode
