hi yuva volume testing is one of the form of performance 
testing.

Performance testing includes 1.Load testing
                             2.Stress testing
                             3.Volume testing 

Volume testing: Testing the application buy putting more 
than the max load to c whether the application bears the 
given load or not i hope it is clear.

Stress Testing:Testing the application buy putting just the 
max load

Load testing:Testing the application buy putting just load 
as requested by the client

Hi friend 
Performance Testing :Here we are testing the performance of
the given software which may includes the size of the
software when installed, the amount of main memory and/ or
secondary storage it requires and the demands made of the
operating system when running within normal limits or the
response time. 

Definition: 
To determine whether the program meets its performance
requirements.
The IEEE standard defines performance testing as testing
concluded to evaluate the compliance of a system or
component with specified performance requirements.
Many programs have specific performance efficiency objectives.
Performance test focuses on performance parameters such as :-
-	Transaction response time.
-	Throughput etc.
e.g.:- in database system the response time relates is the
time to obtain report after checking in a specific button.


The time related features within the performance testing are:
Response time 
Throughput (Slide time delay)

Performances Testing includes 
1.Load testing
2.Stress testing

Load testing:Load testing is performed to test 
How much load a system can withstand?
How system performs as load increases i.e. its response time
throughout system crashes.

Stress Testing :Stress testing is performed to test 
Stress testing is subjecting a system to an unreasonable
load while denying it the resources (e.g. RAM, Disc, CPU,
network, bandwidth, etc) needed to process that load.
The idea is to stress a system to the breaking point in
order to find bugs that will make that break potentially
harmful.
The system is not expected to process the overload without
adequate resource but to behave (e.g. fail) in a decent
manner (e.g. not corrupting or losing data).
Bugs & failures modes discovered under stress testing may or
may not be repaired depending on the application, the
failure mode, consequences, etc. The load (incoming
transaction stream) in stress testing is often deliberately
distorted so as to face the system into resource depletion.

VOLUME TESTING : To determine whether the program can handle
the required volume of data or not.