Parallel queries for a web-application |performance testing

Hello,I will have a web application having postgres 8.4+ as backend. At any given time, there will be max of 1000 parallel web-users interacting with the database (read/write)I wish to do performance testing of 1000 simultaneous read/write to the database.
I can do a simple unix script on the postgres server and have parallel updates fired for example with an ampersand at the end. Example:
echo '\timing \\update "DAPP".emp_data set f1 = 123where emp_id =0;' | "psql" test1 postgres|grep "Time:"|cut -d' ' -f2- >> "/home/user/Documents/temp/logs/$NUM.txt" &pid1=$! echo '\timing \\update "DAPP".emp_data set f1 = 123 where emp_id =2;' | "psql" test1 postgres|grep "Time:"|cut -d' ' -f2- >> "/home/user/Documents/temp/logs/$NUM.txt" &pid2=$! echo '\timing \\update "DAPP".emp_data set f1 = 123 where emp_id =4;' | "psql" test1 postgres|grep "Time:"|cut -d' ' -f2- >> "/home/user/Documents/temp/logs/$NUM.txt" &pid3=$! .............

My question is:Am I losing something by firing these queries directly off the server and should I look at firing the queries from different IP address (as it would happen in a web application). Would the way postgres opens sockets/allocates buffer etc change in the two approaches and I get non-realistic results by a unix script on the server ?It will be very tedious exercise to have 1000 different machines (IP address) and each firing a query; all the same time. But at the same time, I want to be absolutely sure my test would give the same result in production (requirements for latency for read/write is very very low)I am not interested in the network time; just the database read/write time.

Thanks for any tips !-Bala

_________________________________________________________________
The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with Hotmail.
http://www.windowslive.com/campaign/thenewbusy?tile=multicalendar&ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_5