A ODROID forum user @linuxest reported the most affordable 8TB external storage could work with XU4 UAS driver in Kernel 4.9.
I also wanted to make my own NAS because my Google Cloud storage was almost full.
I ordered the same storage(STEB8000100) from Amazon. It is US$180 only. 1TB costs $22 approximately.
It has arrived here this morning and I have run a few samba performance test with kernel 4.9 on my xu4q. I formatted the storage with EXT4 file system before testing because its stock file system is NTFS.
Downloading an 8GB file to my laptop from the XU4 NAS. It shows 110MB/sec of transfer speed stably.
Uploading an 8GB file to the XU4 NAS from my Windows laptop. It shows 90~100MB/sec of transfer speed.
Helios LanTest (3GB transfer option) also shows good performance too.
How to Assemble !
XU4Q and the official case
Velcro tape (3M Scotch 40mm x 25mm 4-pairs)
Attach Velcro tape (loop side) to the XU4Q case bottom
Attach Velcro tape (hook side) to the Seagate HDD case
Place the XU4Q case on the HDD case
DC plug for HDD, DC plug for XU4Q, Ethernet and USB 3.0 cables.