Read/Write to External Drive connected to NAS from networked computer. Possible?

You can share a USB-connected drive on the NAS, although at least one poster has had trouble with HFS+ formatted disks.

You do need at least on internal drive installed on the NAS.

I don't think this is the best approach to sharing, I think it is better to copy the information to the NAS internal drives.

I have a 2TB USB drive attached to my RN102 - it's about the only thing that still works on it though the backup feature no longer works!!) and can access it anywhere on my network via my three Macs.

I found that the only format which works with the file sizes I use is NTFS but you will need a third party application such as Paragon NTFS or Tuxera NTFS if you ever want to write to the USB drive connected directly to a Mac. I would use the ReadyNAS to format the drive because although the Mac can format NTFS, the ReadyNAS would frequently present issues with permissions and often even if files copied, they would either not open or would be write only and the permissions could not be edited.

I can understand why you would want to do this because having had a ReadyNAS Duo brick on me, I was left with two HDDs full of data which I could not access without finding another similar device. I tried installing Linux but even after spending a week at it and buying SATA cables and power supplies, all I could access was what appeared to be aliases to the files and consequently, I lost a lot of data. So, now, ironically, until recently, I was backing up my ReadyNAS to my USB drive in case it happened again. Unfortunately, my RN102 is as useful as a string bag for storing data now.