Two of them side-by-side should fit on a shelf I'm not using 10G so I'm not sure if it'd be able to saturate it. I know from large file transfers I am saturating 1G though, because the file transfer quickly hits peak and just holds there. I am using WD Reds which are 5900rpm and I dunno in theory if they'd even saturate a single SATA link let alone a 10G link. Edit: so I checked the following review - https://www.storagereview.com/wd_red_4tb_hdd_review_wd40efrx - which on the 128k benchmarks suggests 146,000bps which for the sake of easy maths I'll assume is 145MBps. We know that a 1Gbps link will drive upto 125MBps. Assuming you have four hard drives and you're accessing files independently and the PCI-E bus is capable of getting the data out correctly, and you're using 4 x WD Red drives, you're going to be able to push 500MBps or 4Gbps. So if you're going to be doing mirrors you're only ever going to be pushing 250MBps or 2Gbps - you might as well just use the two onboard ports in an etherchannel bonded link, maybe using a HBA or RAID card with a SATA power Y splitter so you can squeeze two 2.5" drives in the top bay instead of the optical drive. You'll be about on par there I guess. Long and short if you really want enough parallelism that pushing the data off multiple hard drives is going to multiplex you up to 10Gbps, and you really don't want to homebrew it because the software isn't where you want it to be, then something like a Synology, expense aside, is likely where you're at.