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From Jonathan Ellis <>
Subject Re: Cluster-wide pause
Date Wed, 30 Jun 2010 05:58:15 GMT
You could be seeing GC pauses. Did you increase the heap size you gave
Cassandra, when you increased your VM size?

On Tue, Jun 29, 2010 at 11:57 AM, Oren Benjamin <> wrote:
> Hi all - first timer here.
> I'm experimenting with Cassandra on Rackspace Cloud.  Started with 4GB nodes and saw
read latency spikes while streaming was taking place, so I increased to 8GB to see if limited
memory was the issue.  Now I'm seeing very strange behavior during any period that writes
are taking place.  The entire (6 node) cluster seems to pause for periods of as much as 5-8
sec.  By that I mean all the stats (cpu, disk, network IO monitored via dstat) drop to zero
or near zero on all nodes simultaneously.  Does anyone have experience with Cassandra on
Rackspace or any idea what's going on here?
> The pauses are short enough that it's difficult to introspect the application and determine
what it's doing during the pause, but long enough to cause unacceptable latency for any service
built on top of it.
> Any ideas or debugging methods would be greatly appreciated,
>  -- Oren

Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano, the source for professional Cassandra support

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