Testing the Performance of the application is best done by
using automated tools.If we plan to do it manually we will
be requiring huge amount of man power resources , Hardware
requirements. Inspite of spending so much money in resources
we will not be able to get accurate result as we can achieve
in automated testing. when we manually give a command to
send a request there may be millisecond of delay between
every user which can be cruicial to the application

i think perfomancetesting by manually is typical,for that 
generally we use tool like LoadRunner ,in that we have 
virtual usergenerator ,with the help of that we can test 
the application with customer expected load

Yes, performance testing can be done through manual testing.
During Beta phase, the application is really in the 
production envirnoment. But you need a tool to trace the 
performance and bench mark it.

But every application does not go through Beta testing. 
Hence automation and performan tool / test suite is the 
best way to test the performance before the application 
goes in to the production envirnoment.

in this testing first we have to create the vertual users in
server as per the claint requirements(in case sort of man
power) than we test the performance of build by all users at
a time