According to AJA Data Calc, a 2K-1556 files at 23.98 with a ProRes422 (HQ) codec is 38.10 MB/sec.
So eight streams of that is 304.8 MB/sec. Any modern 10G connection will give you about 800 MB/sec (unless you are using the Sonnet Solo 10G T2, which is only about 400 MB/sec), but now you have to talk about TOTAL AGGREGATE BANDWIDTH. SO - if you have 3 users, all doing 304 MB/sec, that is about 900 MB/sec total aggregate bandwidth.
Any modern 12 bay or 16 bay RAID array with 7200 RPM drives will provide this for you.
ProMax makes very nice equipment, and can do exactly what you want. The cheapest equivalent QNAP system is the TS-1685. This is a 12 bay with dual 10G ethernet ports. This product costs under $3000. If you put in 12 10TB Seagate Ironwolf drives (about $280 each), you will have 120 TB raw, and 100 TB after RAID 6. Your total aggregate bandwidth with 7200 RPM SATA drives is about 1200 MB/sec total. If you move up to a 16 bay RAID chassis, your bandwidth will increase to about 1600 - 1800 MB/sec total aggregate bandwidth. So going with a 16 bay single static RAID volume will give you more overhead, and less likelyhood of getting stuttering video.
With all of that said - be it ProMax or QNAP, or Studio Network Solutions, or EditShare, or Facilis or AVID Nexis - who in their right minds is doing an 8 camera multicam job with full res 2K media. This workflow is just stupid. Their post production supervisor must be 26 years old.
With the ProMax, you will connect your computers to thunderbolt 2 to 10G adaptors. My suggestion is the Sonnet Solo 10G T2, which is $199, but limited to about 400 MB/sec, or the more expensive Sonnet Twin 10G, which is $495 and will give you 800 MB/sec bandwidth. For the ProMax, you will connect directly to a multiport 10G card on the rear of the ProMax chassis. (this method is also used by Studio Network Solutions and LumaForge). For the QNAP, you will link aggregate the two 10G ports to a Negear XS708T managed switch (about $600) and the Sonnet 10G adaptors from each computer will connect to the Netgear switch.