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From aaron morton <aa...@thelastpickle.com>
Subject Re: Key cache hit rate issue
Date Tue, 14 Feb 2012 23:42:44 GMT
Out of interest what does cfstats say about the bloom filter stats ? A high false positive
could lead to a low key cache hit rate.

> Also, is there a way to warm start the key cache, meaning pre-load the amount of keys
I set as keys_cached?

See key_cache_save_period when creating the CF.

Cheers


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

On 15/02/2012, at 5:54 AM, Eran Chinthaka Withana wrote:

> Hi,
> 
> I'm using Cassandra 1.0.7 and I've set the keys_cached to about 80% (using the numerical
values). This is visible in cfstats too. But I'm getting less than 20% (or sometimes even
0%) key cache hit rate. Well, the data access pattern is not the issue here as I know they
are retrieving the same row multiple times. I'm using hector client with dynamic load balancing
policy with consistency ONE for both reads and writes. Any ideas on how to find the issue
and fix this?
> 
> Here is what I see on cfstats.
> 
> Key cache capacity: 16637958
> Key cache size: 16637958
> Key cache hit rate: 0.045454545454545456
> 
> Also, is there a way to warm start the key cache, meaning pre-load the amount of keys
I set as keys_cached?
> 
> Thanks,
> Eran


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