incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Michael Theroux <mthero...@yahoo.com>
Subject Re: Bloom filters and LCS
Date Fri, 08 Mar 2013 14:04:27 GMT
I think my impression that Bloom Filters were off in 1.1.9 was a misinterpretation of this
thread:

http://www.mail-archive.com/user@cassandra.apache.org/msg27787.html

and this bug:

https://issues.apache.org/jira/browse/CASSANDRA-5029

I read it that Bloom filters were added to 1.2.2 for Bloomfilters, but apparently after being
shutoff in an earlier version of 1.2?

-Mike



On Mar 7, 2013, at 4:48 PM, Edward Capriolo wrote:

> 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.
> 
> Edward
> 
> On Thu, Mar 7, 2013 at 4:30 PM, Wei Zhu <wz1975@yahoo.com> wrote:
> 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:
> 
> https://issues.apache.org/jira/browse/CASSANDRA-4876
> https://issues.apache.org/jira/browse/CASSANDRA-5029
> 
> Looks like in 1.2, it defaults at 0.1, not sure about 1.1.X
> 
> -Wei
> 
> ----- Original Message -----
> From: "Michael Theroux" <mtheroux2@yahoo.com>
> To: user@cassandra.apache.org
> Sent: Thursday, March 7, 2013 1:18:38 PM
> Subject: Bloom filters and LCS
> 
> 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
> 
> 
> 
> 


Mime
View raw message