Enterprise Vault PST Export job [Very Important]

I stuck in trouble that all of exporting PST job was failed.

all of exporting jobs Repeatdly failed. ㅠ.ㅠ

So, Question is

1. How many jobs can run at one time?

my server : HP DL380 G7, 24GB memory,

                windows server 2008 r2,   Enterprise Vault 10.0.4 version

2. How many items can run at one time?

10,000?

20,000?

30,000? 

100,000?

200,000?  

over???

Our enviroment great portion of people  have over 100,000 items and so big mail box.

Our EV PST migration project term is very short.

But our mail data is so big (over 19TB)

 I must export PST data until 8/30. 

please give to me wise answere for my question~~~~~