Question : I tried different Metatrader 4 trading terminals from two different brokers and the volume data is different in both the trading terminals at the same time. Does the broker use different feeds or that volume is only for that particular broker only.

 
In MetaTrader 4 Client Terminal, the volume of bar is the amount of ticks that have income during the bar forming. So, indicator Volume is based on the volume of bars. A tick represents a trading transaction. So in a 1minute charts if 79 transactions occured then the volume is represented as 79. And mostly tick is broker dependent.The absolute average number of ticks is different between brokers. If the market liquidity is high then volumes also high. For Example Alpari UK simply has “volume spikes” not present on the other brokers due to poor liquidity conditions. In general Metatrader doesnt supports tick based charts. visit here to setup Tick Charts for Metatrader 4

What is the impact of Tick Volume?

So if you are trading based on Volume based indicators like Volume Profile, On Balance Volume, Money Flow Index, Force Index or if you are planning for using EA which uses volume information behind your mathematical models be clear what you are exactly planning to do. If you are taking trading decisions based on volume based indicators it is better choose high liquid brokers in live accounts (as demo accounts will provide you different volume picture).

And in case of CFD trading the volume information represents broker based Tick Volume and not the actuals future contracts/number of stock traded in the exchange. So in such scenarios its better to avoid volume based studies in your trading decision.