I read that the change was made because Cassandra does not work well when they are off. This makes sense because cassandra uses bloom filters to decide if a row can be deleted without major compaction. However since LCS does not major compact without bloom filters you can end up in cases where rows never get deleted.
On Thu, Mar 7, 2013 at 4:30 PM, Wei Zhu <email@example.com>
Where did you read that bloom filters are off for LCS on 1.1.9?
Those are the two issues I can find regarding this matter:
Looks like in 1.2, it defaults at 0.1, not sure about 1.1.X
----- Original Message -----
From: "Michael Theroux" <firstname.lastname@example.org>
Sent: Thursday, March 7, 2013 1:18:38 PM
Subject: Bloom filters and LCS
(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