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From Michael Theroux <>
Subject Bloom filters and LCS
Date Thu, 07 Mar 2013 21:18:38 GMT

(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


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