Riak memory usage higher than expected

Jacques whshub at gmail.com
Tue Aug 16 15:09:56 EDT 2011


We're utilizing Riak 14.2 and we're seeing higher memory consumption than we
expect.

We're running on a 4 node cluster with each node housing 32gb of memory and
are utilizing bitcask with a 3x write replication factor.  We're seeing
faster growth than we expect and also seeing weird bounces update.

You can see an example chart <http://picturepush.com/public/6331935>.
 (note, there are sometimes where we've had to stop the job for short
periods of time-- you can see these as flat spots).

We are doing a large throttled import that has key sizes of approximately 12
bytes.  We're currently around 450mm unique items and riak memory
consumption is ~110gb.  The input job is probably 95% new puts and 5%
overwriting puts.

According to the capacity planner tools, our key space should probably be
about half what are actual memory consumption is.

As you can see in the chart, we're also seeing jumps in memory size at
random intervals.  What might these be?  Nothing interesting in the logs
that I can see.  Regular merges.

A close up <http://picturepush.com/public/6332084> of a recent jump in
memory consumption for one of the nodes (they all look the same).  There are
no corresponding distinct patterns within the cpu chart.  Things are pretty
flat although we have more wait sometimes than we like (need more spindles
clearly).


Any helpful thoughts?

Thanks,
Jacques
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