Thanks for this, really interesting stuff.  Just to make sure I'm understanding it, this is for PHP clients witha  1 second timeout and retry is to a different  node in the cluster with the same timeout.  Have you enabled the Dynamic Snitch ? http://www.riptano.com/blog/whats-new-cassandra-065 Aaron On 22 Sep, 2010,at 01:29 AM, Juho Mäkinen wrote: It's known that compaction hurts the node performance so that it might miss some requests. That's why it's important to handle these situations and the client needs to retry the operation into another working host. We have been storing performance data from each cassandra request which we do into our five node cassandra production cluster. We log the retry count and request type into our data warehouse solution and I've now extracted the data from a 10 day period and calculated how many retry requests is needed so that the results can be obtained. The following chart tells how many time an operation had to be retried until it was successfully completed. The percents tells the probability like that "the request will be successful with the first try in 99.933 % times." Total amount of operations: 94 682 251 within 10 days. Retry times | operations | percentage from total operations 0 | 94618468 | 99.93263 % 1 | 56688 | 0.05987 % 2 | 5018 | 0.00529 % 3 | 1359 | 0.00144 % 4 | 111 | 0.00012 % 5 | 25 | 0.00003 % There were also few operations which needed more than five retries, so preparing to try up to ten times is not a bad idea. The cluster users 0.6.5 with RF=3. Each operation is executed until it succeeds or until 10 retries using this php wrapper http://github.com/dynamoid/cassandra-utilities Have others found similar results? Please discuss :) - Juho Mäkinen