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From Jan Algermissen <jan.algermis...@nordsc.com>
Subject Re: Throughput and RAM
Date Tue, 10 Sep 2013 20:28:13 GMT

On 10.09.2013, at 19:37, Robert Coli <rcoli@eventbrite.com> wrote:

> "Cassandra does not prevent a given node from writing to RAM faster than it can flush
to disk"? 

Yes, that is what I meant.

What remains unclear to me is what the oprational strategy is towards handling an increase
in writes or peaks.

Seems to be: "wait until nodes die and then add capacity".

I guess what I am looking for is the switch so that *I* can tell C* not to write more to RAM
than it is able to flush.

I have a hunch that coordinators pile up incoming requests and that the memory used by them
causes the node to stop flushing completely.

I tried to reduce rpc connections and/or reduce write timeouts but both hadd no effect.

Can anybody provide a direction in which to look?

This image ( http://twitpic.com/dcwlmn)  shows the typical situation for me, no matter what
switches I work with. There is always this segment of an arc which shows  the increasing unflushed
memtables.

Jan
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