USB Flashdrive

Every USB Drive I've ever tried has worked for this so I don't think it matters.  I've used form 3 GB to 32 GB, no problem.  If the drive you are using has a ton of files on it it may take 30 seconds or more for the Ion to recognise it so be patient.

I haven't extensively tested drives, but every one that I've used has worked without issue. Just make sure that when removing your drive you wait a good 30 seconds after the save has completed before removing the drive... Otherwise you can end up with corrupt show files.

This has to do with the way windows works with USB drives, and while windows will report to EOS that the save is complete, it actually is still doing stuff, and premature removal can cause corruption.