A problem with thunderbolt 3 and FCP X is driving me nuts and was looking towards your wisdom and experiences to help track this issue down. Mounting the NAS via Thunderbolt 3 (40G cable/SMB 3) and trying to create/name/delete a new folder inside an FCPX event, or even attempting playback (normal HD H.264 files from a Canon 5Dmk3) I get beachballs all the time. This is on a fresh install of High Sierra 10.13.3 and on the Macbook Pro 15" 2017 with Touchbar. Library and footage is on the NAS and SMB signing is disabled. When mounting to the same exact location via a normal 1Gbps Ethernet cable (and smb 3) everything runs smooth as butter! I've created a short video of the problem. Perhaps with your knowledge you can help in figuring out a solution. I've tried almost every trick in the book. Is this the case for you as well via Thunderbolt 3/10GbE? (In the video when I say SD footage I mean HD )
Although I have not tested Thunderbolt Networking lately, every time I did, direct thunderbolt networking was unreliable and not better than what you are demonstrating (maybe NFS would be better?). All satisfied people I have read about were using 10GbE via a Thunderbolt box...
Maybe some other could chime in. I will for my self stick with ethernet networking.
For anyone following this, the slowdown issues seem to be resolved in the latest macOS 10.13.4. I have been in contact with both QNAP and Apple and before today the issue was ongoing. We can now work on the system again with multiple users. For reference I will post the configuration that is working for me:
FCPX 10.4, macOS 10.13.4
MacBook Pro Retina 2017 15" Maxed out
QNAP TVS-1282T3 firmware 4.3.4.0537 Build 20180331
QNAP's 40Gbps 2m Thunderbolt 3 cable
8x8TB HGST NAS 7200rpm drives
1 Static volume (Qsirch on, spotlight indexing on, multimedia apps off, network trash off)
Mounting via SMB 3
iMac 5K Retina & Mac Pro 2008 (with dosdude's patch to install 10.13.4 and an NVIDIA GTX 960) connected via 1Gbps ethernet for now. Waiting on NAB for new 10Gbps adapters.
You may not want to read the following if you require a direct thunderbolt 3 connection. For me, I needed to put the machine somewhere quiet and so 10GBe was the way to go.The first thing I did was buy Sonnet's Solo 10G (Thunderbolt 3 to 10GBe) which is rock solid btw in Catalina - in comparison to Apple's built-in 10GBe ports that cause disconnects upon heavy load. The latter was also the reason I wasn't upgrading to Catalina all this time. And Catalina has been a big upgrade on SMB 3 speeds (and a downgrade to many other things!). However up to Mojave I could only get around 800MB/s Read/400MB/s Write, where as with the same hardware and Windows (bootcamp) I could get 1000MB/s Read. Catalina optimised this and I get 980R/600W. Nowadays I don't force spotlight indexing by the OS. They had added built in support for spotlight search (only files, not folders), but since late Mojave this broke, and QNAP haven't addressed it yet although multiple tickets have been opened the past year.