On Nov 22, 2009, at 8:54 AM, Ryan Chan wrote:
> Is it common heard from people that if you have large table (assume
> MyISAM in my case), you need large memory in order to have the
> key/index in memory for performance, otherwise, table scan on disk is
> But how to estimate how much memory I need?
> Consider a simple case, a MyISAM table is 10GB in size, with 2GB
> index, how much memory I need?
It's not the size of the table, it's the size of the index that you
need to watch. MyISAM keeps the table and index separate, so the
memory requirements can be considerably less than the size of the
table. What you have likely heard is in reference to InnoDB tables.
Since InnoDB "clusters" the index with the data, the memory
requirements can be much greater. You may notice a significant drop
off in performance from InnoDB once the data size passes a certain
level, which is based on your RAM and InnoDB settings.
MyISAM performance is usually fairy steady as the size of the table