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From Héctor Izquierdo Seliva <izquie...@strands.com>
Subject Re: Index interval tuning
Date Wed, 11 May 2011 10:44:36 GMT
Sorry aaron, here are the values you requested

RecentBloomFilterFalsePositives = 5;
BloomFilterFalsePositives = 385260;

uptime of the node is three days and a half, more or less


El mié, 11-05-2011 a las 22:05 +1200, aaron morton escribió:

> What are the values for RecentBloomFilterFalsePositives and BloomFilterFalsePositives
the non ratio ones ?
>  
> -----------------
> Aaron Morton
> Freelance Cassandra Developer
> @aaronmorton
> http://www.thelastpickle.com
> 
> On 11 May 2011, at 19:53, Héctor Izquierdo Seliva wrote:
> 
> > El mié, 11-05-2011 a las 14:24 +1200, aaron morton escribió:
> >> What version and what were the values for RecentBloomFilterFalsePositives and
BloomFilterFalsePositives ?
> >> 
> >> The bloom filter metrics are updated in SSTableReader.getPosition() the only
slightly odd thing I can see is that we do not count a key cache hit a a true positive for
the bloom filter. If there were a lot of key cache hits and a few false positives the ratio
would be wrong. I'll ask around, does not seem to apply to Hectors case though. 
> >> 
> >> Cheers
> > 
> > 0.7.5, and I am no longer using key cache. I get the bloom filter stats
> > via jmx. BloomFilterFalsePositiveRatio is always stuck at 1.0.
> > RecentBloomFilterFalsePositiveRation fluctuates from 0 to 1.0 with no
> > intermediate values. 
> > 
> > As for the index interval settings, I changed it from 128 to 256 and
> > memory consumption was just a tad lower but read performance was worse
> > by a few ms, so not much to gain there.
> > 
> >> -----------------
> >> Aaron Morton
> >> Freelance Cassandra Developer
> >> @aaronmorton
> >> http://www.thelastpickle.com
> >> 
> >> On 11 May 2011, at 10:38, Chris Burroughs wrote:
> >> 
> >>> On 05/10/2011 02:12 PM, Peter Schuller wrote:
> >>>>> That reminds me, my false positive ration is stuck at 1.0, so I
guess
> >>>>> bloom filters aren't doing a lot for me.
> >>>> 
> >>>> That sounds unlikely unless you're hitting some edge case like reading
> >>>> a particular row that happened to be a collision, and only that row.
> >>>> This is from JMX stats on the column family store?
> >>>> 
> >>> 
> >>> (From jmx)  I also see BloomFilterFalseRatio stuck at 1.0 on my
> >>> production nodes.  The only values that RecentBloomFilterFalseRatio had
> >>> over the past several minutes were 0.0 and 1.0.  While I can't prove
> >>> that isn't accurate, it is very suspicions.
> >>> 
> >>> The code looked reasonable until I got to SSTableReader, which was too
> >>> complicated to just glance through.
> >> 
> > 
> > 
> 



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