Primary or Logical for USB backup

[brother]

Hi, I have an external USB hard drive. I would like to use it, with Acronis 2010,
for the backup images of my Windows 7 premium 64bit.
Should I make it a logical drive? or a primary?
Would it make any difference if I had to boot up from a recovery DVD to be able to find and locate the USB drive?
Thanks in advance !
Graham

 

[Minotar]

Id set it as primary and assign a Letter sio Win7 can see it.