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From Jeff Jirsa <jeff.ji...@crowdstrike.com>
Subject Re: Bloom filter memory usage disparity
Date Wed, 18 May 2016 03:18:56 GMT
Even with the same data, bloom filter is based on sstables. If your compaction behaves differently
on 2 nodes than the third, your bloom filter RAM usage may be different.


From:  Kai Wang
Reply-To:  "user@cassandra.apache.org"
Date:  Tuesday, May 17, 2016 at 8:02 PM
To:  "user@cassandra.apache.org"
Subject:  Re: Bloom filter memory usage disparity

Alain,

Thanks for replying.

I am using C* 2.2.4. 
Yes the table is RF=3. 
I changed bloom_filter_fp_chance from 0.01 to 0.1 a couple of months ago.


On Tue, May 17, 2016 at 11:05 AM, Alain RODRIGUEZ <arodrime@gmail.com> wrote:
Hi, we would need more information here (if you did not solve it yet). 

What is your Cassandra version?
Does this 3 node cluster use a Replication Factor of 3?
Did you change the bloom_filter_fp_chance recently?

That table has about 16M keys and 140GB of data.

Is that the total value or per node? In any case, we need the data size for the 3 nodes to
understand.

It might have been a temporary situation, but in this case you would know by now.

C*heers,


2016-05-03 18:47 GMT+02:00 Kai Wang <depend@gmail.com>:
Hi,

I have a table on 3-node cluster. I notice bloom filter memory usage are very different on
one of the node. For a given table, I checked CassandraMetricsRegistry$JmxGauge.[table]_BloomFilterOffHeapMemoryUsed.Value.
2 of 3 nodes show 1.5GB while the other shows 2.5 GB.

What could be the reason?

That table is using LCS. 
bloom_filter_fp_chance=0.1
That table has about 16M keys and 140GB of data.

Thanks.




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