EV will increase Outlook OST size ???

Hi All,

    We are using EV 9.0 and currently we are facing some issues with outlook.

All our Exchange users enable with EV Archive and all the users are using outlook 2010 SP1 with caching mode.  I verified users OST file and it’s compare to exchange mailbox size OST size is double.

Find the below sample mail box size details.

EV Archive enable mailbox with short cut.

 Exchange mailbox size: 500 MB

 Client OST file size       : 1.3 GB

Without Archive mailbox

Exchange mailbox size: 500 MB

Client OST file size       : 700 MB

I want to make sure EV increasing the OST files size or not? 

if anyone have idea please share with me.