104 backup individual folders from external USB drive?

One approach is to connect the drive to your PC, and copy it over the network.

my pc is terrible though, and only gets about 20MB/s on the network when transferring files! windows estimates that that wat would take at least 6 hours so would rather not! :(

The RN104 peaks out at 50 MB/s write speed, so it will take time no matter how you do it.

is that over the network too!?
one of the main reasons i bought this unit was so i could use the USB port like i'm trying to... the fact that i can't and its limited to 50MBps means its looking like i'll send it back!

50 MBs is the write speed over a gigabit network - reads are faster. If you need ~100 MBs write speeds you need an RN314.

You can use the USB port, though you need to get the path correct. I generally don't use it, and am not at the machine right now - and don't want to give you mis-information.

The 104 is not limited by software, but it has a really weak CPU. Mine peaks at around 100MBytes/s via SMB in read, and around 50Mbytes/s in write no matter the protocol, I don't have numbers for USB direct copy but should be around that too. You might be able to speed up the write speed by plugging an UPS and disabling some security protocols designed to protect you data in case of a power failure.
50Mbytes/s is the most you can get from USB2 drives anyway (max USB2 speed is 480mbits/s, makes 60Mbytes/s and there is always some loss between real and theorical speeds), and most USB3 drives won't go any higher because they tend to use cheap 5400RPM 2.5 inches drives on "mobile" models.

You can copy through a PC using network (gigabit connection recommended). You should be able to copy through GUI using the "browse" function and right clicking copy then paste (I think it will be slower than PC though). Another option is to enable SSH and directly copy from linux command line if you know what you are doing.
Backup utility doesn't seem to let you select the path for USB...

USB access is slower than network access. Even the RN314 only writes to USB 3.0 drives at about 17 MBs. Not sure about reads, smallnetbuilder didn't measure them in their review.

ReadyNAS are optimized for network transfers, USB speeds are pretty slow on all the platforms.

I was wrong saying I had no real numbers for USB, I just remembered doing some tests for another post long ago. I totally forgot this post, but it came right in my mind when I packed the USB disk I used for the test (A friend needs a temporary backup for reinstalling his OS). But yes you are right it was slower on my external HDD (2.5", 7200RPM, USB2), but this disk seemed to get only to 27Mbytes/s on windows so I took this was a drive limitation.
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