[Jax.PM] MySQL ?

[Steve Lane]

"William C (Bill) Jones" wrote:
> 
> >> What values would you give
> >>
> >> KEY_BUFFER=???
> >> TABLE_CACHE=???
> >> JOIN_BUFFER=???
> >> RECORD_BUFFER=???
> >> SORT_BUFFER=???
> >> MAX_CONNECTIONS=300
> >> TMP_TABLE_SIZE=???
> >>
> >> Knowing you have 6GB RAM 6GB Swap and want to handle 300 connections and be
> >> very very fast (heck, I got 4 CPUs dedicated to this :/  :)
> >
> > just from experience, you'll probably gain more performance
> > by concentrating on your table design, and how to handle
> > expensive queries, and table locking, than from the variables.
> 
> Unfortunately I had no design control over the system (Blackboard) - but was
> definitely interested in what other are doing, etc.
> 
> Maybe I should say I want to handle 250 httpd and 300-500 mysql connections
> per second (simultaneously -- whatever that means these days.)

Blackboard sucks.  anyway...

someone else asked about if you're using mod_perl and Apache::DBI
(to cache the database connections).  both are important factors.
mod_perl will (or should) speed things up a lot, but it'll also
increase the size of the httpd's, sometimes dramatically, depending
on what (Perl) modules are in the httpd's.  and of course what part
of the httpd's are shared memory (if i said that right; i'm not
quite yet a memory-usage guru).

example: you've got 250 httpd's, each using 30 Mb unshared memory
(not atypical for a mod_perl server with a kazillion loaded Perl
modules).  that's 7.5 Gb memory!  and we haven't even counted the
mysqld's yet... but they'll typically be <5 Mb.

to sum up, i don't think your mysqld-variable tuning's gonna have
much effect.  or at least, other things are gonna have a lot more
effect.
--
Steve Lane <sml at zfx.com>