This thread hasn't seen a new post for a year, so I don't know if anyone will read this
I too bought one of these units and was devastated when I tried copying to the HHD.
Here's what I'm doing now:
I have two methods.
Method #1 (50MB/sec)
I pull the HDD out of the AIOS and plug it into an external USB 3 Adapter. I now plug the adapter into a USB 3 port on my PC. Acceptable speeds are achieved when only copying 50GB of data.
Method # 2 (True SATA III 6GB/sec)
One of my PCs has a convenient little opening where I simply pulled a SATA III data and power cable thru. I keep them capped with rubber sleeves when not in use. I simply shut down my PC, take the 3TB HDD (NTFS format) out of my AIOS, plug it in to the cables and fire up the PC. I now copy files to the HDD with blazing speeds.
Yes, I have to connect and disconnect with my PC off, but when I can copy 800 GB to the HDD in less than an hour, the (2) boot trade-off is well worth it.
I hope I've help someone else with this info.