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From Robert Coli <rc...@digg.com>
Subject Re: read latency in cassandra
Date Wed, 09 Feb 2011 20:50:12 GMT
On Fri, Feb 4, 2011 at 11:13 AM, Dan Kuebrich <dan.kuebrich@gmail.com> wrote:
> Is 2 seconds the normal "I went to disk" latency for cassandra?

Cassandra exposes metrics on a per-CF basis which indicate latency.
This includes both cache hits and misses, as well as requests for rows
which do not exist. It does NOT include an assortment of other latency
causing things, like thrift.

If you see two seconds of latency from the perspective of your
application, you should compare it to the latency numbers Cassandra
reports. If you are getting timed-out exceptions, that does seem
relatively likely to be the cold cache "I went to disk" case, and the
Cassandra latency numbers should reflect that.

=Rob

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