It was found out that that having no bloom filter is a bad idea because it causes issues where deleted rows are never removed from disk. Newer versions have fixed this. You should adjust your bloom filter settings to be >0 sized.

On Thu, Mar 7, 2013 at 4:18 PM, Michael Theroux <mtheroux2@yahoo.com> wrote:
Hello,

(Hopefully) Quick question.

We are running Cassandra 1.1.9.

I recently converted some tables from Size tiered to Leveled Compaction.  The amount of space for Bloom Filters on these tables went down tremendously (which is expected, LCS in 1.1.9 does not use bloom filters).

However, although its far less, its still using a number of megabytes.  Why is it not zero?


                Column Family: XXXX
                SSTable count: 526
                Space used (live): 7251063348
                Space used (total): 7251063348
                Number of Keys (estimate): 23895552
                Memtable Columns Count: 45719
                Memtable Data Size: 21207173
                Memtable Switch Count: 579
                Read Count: 21773431
                Read Latency: 4.155 ms.
                Write Count: 16183367
                Write Latency: 0.029 ms.
                Pending Tasks: 0
                Bloom Filter False Positives: 2442
                Bloom Filter False Ratio: 0.00245
                Bloom Filter Space Used: 44674656
                Compacted row minimum size: 73
                Compacted row maximum size: 105778
                Compacted row mean size: 1104

Thanks,
-Mike