memcached performance ?

[globot]

hi,

I am a new user of memcached... and want to use it for massive data 
exchange on web site, and i would like to know if there are people that 
already run benchmarks for the memcached deamon ?
I want to know if this system could handle huge amount of connection (if 
i set connection limit to 1 million and there is at 30000 get/s + 3000 
set/s, is it ok ?)... in fact i want to know if i can use one memcached 
(can he hanle it well enought) for one cluster even if i'am almost sure 
it is better to have one per machine and update the cache of each when 
data change...

secondo, i want to know if memcached will introduce lock mecanism (to 
avoid seting data buy to client at the same time) and events 
notification... for exemple a client want to know when a key is 
modified, it could be usefull with a callback function...