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From Mohit Anchlia <mohitanch...@gmail.com>
Subject Re: how to reduce disk read? (and bloom filter performance)
Date Mon, 10 Oct 2011 16:53:12 GMT
Does it mean you are not updating a row or deleting them? Can you look
at JMX values of

BloomFilter* ?

I don't believe bloom filter false positive % value is configurable.
Someone else might be able to throw more light on this.

I believe if you want to keep disk seeks to 1 ssTable you will need to
compact more often.

On Sun, Oct 9, 2011 at 7:09 AM, Radim Kolar <hsn@sendmail.cz> wrote:
> Dne 7.10.2011 23:16, Mohit Anchlia napsal(a):
>>
>> You'll see output like:
>>
>> Offset      SSTables
>> 1                  8021
>> 2                  783
>>
>> Which means 783 read operations accessed 2 SSTables
>
> thank you for explaining it to me. I see this:
>
> Offset      SSTables
> 1              59323
> 2                857
> 3                  56
>
> it means bloom filter failure ratio over 1%. Cassandra in unit tests expects
> bloom filter false positive less than 1.05%. HBase has configurable bloom
> filters. You can choose 1% or 0.5% - it can make difference for large cache.
>
> But result is that my poor read performance should not be caused by bloom
> filters.
>

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