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From Santal Li <>
Subject Re: cassandra freezes
Date Sat, 20 Feb 2010 03:40:46 GMT
I meet almost same thing as you. When I do some benchmarks write test, some
times one Cassandra will freeze and other node will consider it was shutdown
and up after 30+ second. I am using 5 node, each node 8G mem for java heap.

>From my investigate, it was caused by GC thread, because I start the
JConsole and monitor with the memory heap usage, each time when the GC
happend, heap usage will drop down from 6G to 1G, and check the casandra
log, I found the freeze happend at exactly same times.

So I think when using huge memory(>2G), maybe need using some different GC
stratege other than the default one provide by Cassandra lunch script.
Dose't anyone meet this situation, can you please provide some guide?


2010/2/17 Tatu Saloranta <>

> On Tue, Feb 16, 2010 at 6:25 AM, Boris Shulman <> wrote:
> > Hello, I'm running some benchmarks on 2 cassandra nodes each running
> > on 8 cores machine with 16G RAM, 10G for Java heap. I've noticed that
> > during benchmarks with numerous writes cassandra just freeze for
> > several minutes (in those benchmarks I'm writing batches of 10 columns
> > with 1K data each for every key in a single CF). Usually after
> > performing 50K writes I'm getting a TimeOutException and cassandra
> > just freezes. What configuration changes can I make in order to
> > prevent this? Is it possible that my setup just can't handle the load?
> > How can I calculate the number of casandra nodes for a desired load?
> One thing that can cause seeming lockups is garbage collector. So
> enabling GC debug output would be heplful, to see GC activity. Some
> collector (CMS specifically) can stop the system for very long time,
> up to minutes. This is not necessarily the root cause, but is easy to
> rule out.
> Beyond this, getting a stack trace during lockup would make sense.
> That can pinpoint what threads are doing, or what they are blocked on
> in case there is a deadlock or heavy contention on some shared
> resource.
> -+ Tatu +-

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