what external hard drive will work with the surface pro 3

• Edited by Brandon RecordsModerator 11 hours 7 minutes ago Clarified title.

as per suggestion from this site, I suggest you thinking about another option like OneDrive (cloud storage), USB drives (pen drive), and microSD cards

https://www.microsoft.com/surface/en-us/support/storage-files-and-folders/surface-storage-options

this is the tips to free up your disk space

http://windows.microsoft.com/en-us/windows-8/free-up-disk-space

I suggest use external HDD which using less power (external HDD mobile) or powered external HDD, since Surface only have 900ma (4.5v)

• Edited by britishdhez Monday, March 02, 2015 8:29 AM
• Proposed as answer by MeipoXuMicrosoft contingent staff, Moderator Tuesday, March 03, 2015 5:14 AM
• Marked as answer by Brandon RecordsModerator 11 hours 8 minutes ago

I would recommend using an external hard drive that has a separate power source to eliminate the possibility of low power on the USB port causing the drive to appear unreadable. You can read about others who experienced this issue here.

Brandon
Windows Outreach Team- IT Pro
Windows for IT Pros on TechNet