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From Oren Benjamin <>
Subject Cluster-wide pause
Date Tue, 29 Jun 2010 16:57:10 GMT
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
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