Multi threading with mysql Server version: 5.1.49-3 (Debian)

hi
I just configured one debian myql server which will work as master for a high load database.

becasue there would be 3 instances. I configured mysqld_multi with 3 different port.

and it willb e innodb database,.

now few things i want to discuss for the performance

(1) data1, data2  ( for  data directry ) in a different "Array 10" partition
2) innodb_buffer_pool_size= 16GB for each database
3) innodb_thread_concurrency=16
 

now  :

(a)is there any disadvantages of mysqld_multi for high end database ??  ( i did not see an y thing documentation for this so i belived it will be same)
(b) is there any variables to tell mysql to use multi procesosr ?? ( although, it set to us innodb_thread_concurrency=16)

other then

query_cache_size,table_cache,tmp_table_size,thread_cache is there any thing else to increase performance of innodb database ?


i will use mysql_tuner later on .. but i looking for extra advise .. to see what i am missing ..