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From aaron morton <aa...@thelastpickle.com>
Subject Re: Key cache hit rate issue
Date Thu, 16 Feb 2012 08:30:44 GMT
> Its in the order of 261 to 8000 and the ratio is 0.00. But i guess 8000 is bit high. Is
there a way to fix/improve it?
Sorry I don't understand what you mean. But if the ratio is 0.0 all is good. 

Could you include the full output from cfstats for the CF you are looking at ?

Cheers

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

On 15/02/2012, at 1:00 PM, Eran Chinthaka Withana wrote:

> Its in the order of 261 to 8000 and the ratio is 0.00. But i guess 8000 is bit high.
Is there a way to fix/improve it?
> 
> Thanks,
> Eran Chinthaka Withana
> 
> 
> On Tue, Feb 14, 2012 at 3:42 PM, aaron morton <aaron@thelastpickle.com> wrote:
> 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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