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Date: Fri, 21 Dec 2012 12:27:23 +0000
From: James Masson <james.masson@opigram.com>
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Subject: Cassandra read throughput with little/no caching.
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Hi list-users,

We have an application that has a relatively unusual access pattern in 
cassandra 1.1.6

Essentially we read an entire multi hundred megabyte column family 
sequentially (little chance of a cassandra cache hit), perform some 
operations on the data, and write the data back to another column family 
in the same keyspace.

We do about 250 writes/sec and 100 reads/sec during this process. Write 
request latency is about 900 microsecs, read request latency is about 
4000 microsecs.

* First Question: Do these numbers make sense?

read-request latency seems a little high to me, cassandra hasn't had a 
chance to cache this data, but it's likely in the Linux disk cache, 
given the sizing of the node/data/jvm.

thanks

James M