The difference in recommendation size comes from the different
techniques each storage engine uses for caching data. myisam
(key_buffer_size) only stores indexes where innodb_buffer_pool_size
stores both indexes and data. mysiam relies on the operating system to
cache data in ram which is why you don't want to use all available
memory for the key buffer.
On 1/14/06, Grant Giddens <lggiddens@stripped> wrote:
> Hi,
>
> After reading through the example my.cnf files (large, huge, etc), I started to
> wonder what the difference was between the isam key_buffer_size and the innodb
> innodb_buffer_pool_size.
>
> I realize that they are two different table types, but some of the docs says to
> set the key_buffer_size to 25%-50% of the overall system memory. The comments for the
> innodb_buffer_pool_size say that it can be set to 50%-80% of the overall system memory.
>
> Maybe I don't understand exactly the difference between the two because I don't
> understand why they have different memory recommendations.
>
> Is there any FAQs on the my.cnf file? How would you set these two variables if
> you had an even mix of isam and innodb tables? Where can I learn more about tweaking the
> my.cnf file? The mysql online documentation is good, but I need a more basic description
> of these two variables and all the other my.cnf settings.
>
> Thanks,
> Grant
>
>
>
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--
Eric Bergen
eric.bergen@stripped
http://www.ebergen.net
