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From aaron morton <aa...@thelastpickle.com>
Subject Re: Timeout during stress test
Date Tue, 12 Apr 2011 10:44:17 GMT
Couple of hits here, one from jonathan and some previous discussions on the user list http://www.google.co.nz/search?q=cassandra+iostat

Same here for cfhistograms http://www.google.co.nz/search?q=cassandra+cfhistograms 
cfhistograms includes information on the number of sstables read during recent requests. As
your initial cfstats showed 236 sstables I thought it may be useful see if there was a high
number of sstables been accessed per read. 

70 requests per second is slow against a 6 node cluster where each node has 12 cores and 96GB
of ram. Something is not right.

Aaron 
On 12 Apr 2011, at 17:11, mcasandra wrote:

> 
> aaron morton wrote:
>> 
>> You'll need to provide more information, from the TP stats the read stage
>> could not keep up. If the node is not CPU bound then it is probably IO
>> bound. 
>> 
>> 
>> What sort of read?
>> How many columns was it asking for ? 
>> How many columns do the rows have ?
>> Was the test asking for different rows ?
>> How many ops requests per second did it get up to?
>> What do the io stats look like ? 
>> What does nodetool cfhistograms say ?
>> 
> It's simple read of 1M rows with one column of avg size of 200K. Got around
> 70 req per sec.
> 
> Not sure how to intepret the iostats output with things happening async in
> cassandra. Can you give little description on how to interpret it?
> 
> I have posted output of cfstats. Does cfhistograms provide better info?
> 
> 
> --
> View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Timeout-during-stress-test-tp6262430p6263859.html
> Sent from the cassandra-user@incubator.apache.org mailing list archive at Nabble.com.


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