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From David Boxenhorn <da...@taotown.com>
Subject Re: Combining all CFs into one big one
Date Mon, 02 May 2011 17:06:59 GMT
I guess I'm still feeling fuzzy on this because my actual use-case isn't so
black-and-white. I don't have any CFs that are accessed purely, or even
mostly, in once-through batch mode. What I have is CFs with more and less
data, and CFs that are accessed more and less frequently.


On Mon, May 2, 2011 at 7:52 PM, Tyler Hobbs <tyler@datastax.com> wrote:

> On Mon, May 2, 2011 at 5:05 AM, David Boxenhorn <david@taotown.com> wrote:
>
>> Wouldn't it be the case that the once-used rows in your batch process
>> would quickly be traded out of the cache, and replaced by frequently-used
>> rows?
>>
>
> Yes, and you'll pay a cache miss penalty for each of the replacements.
>
>
>> This would be the case even if your batch process goes on for a long time,
>> since caching is done on a row-by-row basis. In effect, it would mean that
>> part of your cache is taken up by the batch process, much as if you
>> dedicated a permanent cache to the batch - except that it isn't permanent,
>> so it's better!
>>
>
> Right, but we didn't want to cache any of the batch CF in the first place,
> because caching that CF is worth very little.  With separate CFs, we could
> explicitly give it no cache.  Now we have no control over how much of the
> cache it evicts.
>
>

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