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From aaron morton <aa...@thelastpickle.com>
Subject Re: Cassandra 1.0.6 data flush query
Date Sun, 24 Jun 2012 18:35:53 GMT
> memtable_total_space_in_mb: 200 
This means cassandra tries to use less than 200MB of real memory to hold memtables. The problem
is java takes a lot more memory to hold data than it takes to store on disk. You can see the
ratio of serialized to live bytes logged from the Memtable with messages like "setting live
ratio…" It can be anywhere from 1 to 64. 

So it the live ratio is 10, your 10MB SSTable is taking 100MB in ram. 

In short, add more ram to the VM. 

Cheers

-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 22/06/2012, at 3:58 PM, Roshan wrote:

> Hi
> 
> I am using Cassandra 1.0.6 version in our production system and noticed that
> Cassandra flushing the data to SSTable and the file size is < 10MB. With
> under moderate write load, the Cassandra flushing lots of memtables with
> small sizes. With this compaction doing lots of compactions.
> 
> O/S - Centos 64bit Sun Java 1.6_31
> VM size - 2.4GB
> 
> Following parameters change on cassandra.yaml file.
> 
> flush_largest_memtables_at: 0.45 (reduce it from .75)
> reduce_cache_sizes_at: 0.55 (reduce it from .85)
> reduce_cache_capacity_to: 0.3 (reduce it from .6)
> concurrent_compactors: 1
> memtable_total_space_in_mb: 200 
> in_memory_compaction_limit_in_mb: 16 (from 64MB)
> Key cache = 10000
> Row cache = 0
> Could someone please help me on this.
> 
> Thanks
> /Roshan
> 
> 
> --
> View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Cassandra-1-0-6-data-flush-query-tp7580733.html
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