[SOLVED] Custom Rackmount eGPU / PCIe 3 / Thunderbolt 3

[james211]

I work in the photo / film industry and I'm in need of something that may not exist. I'm looking to build an ultra portable station that utilizes a Mac mini 2018, an eGPU and an M.2 Raid Card. The closest thing I've found is the Sonnet Echo Express III-R Thunderbolt. The unit runs PCIe x8 over three lanes, but the lanes are divided x8 x4 x4 - which kind of sucks, I'd like at least three that run at x8.

So here are a few questions:

1. Is it possible to build your own? Buy your own backplane, PSU, etc?
2. Does anyone know of any additional options? EDIT: I recently stumbled on this, waiting for further info from them

 

[velocityg4]

Note that these descriptions are misleading. Take the Sonnet for instance. It provide 3 PCIe 3.0 slots. Two of which are mechanically x8 and electrically x4. While the third is mechanically x16 and electrically x8.

These are just the connections to the cards. It only has one Thunderbolt 3 connection to the computer. Which means all connected devices are splitting the equivalent of a PCIe 3.0 x4 connection. While this may be fine to share SSD and network connections. I would not want to also share an eGPU on that port. PCIe 3.0 x4 is enough of a bottleneck for an eGPU as it is.

It is a shame as the Mac Mini (2018) has two Thunderbolt 3 controllers. Rather than just using one Thunderbolt 3 connection to the Mac. They could have used both connections for the equivalent of a PCIe 3.0 x8 connection to the Mac. The second Thunderbolt 3 port on these rack mounts is for daisy chaining.

I'd say that for what you are looking to do. The optimal option would be to buy an empty Rack mount chassis. Then get two Thunderbolt 3 PCIe enclosures. A cheaper low powered model for your external SSD, RAID, &c. Then one with a powerful PSU dedicated for an eGPU. Then stick everything in the Rack chassis

Also for the NVMe RAID. You'll be limited by the Thunderbolt 3 connection. Many NVMe won't be much faster than one good NVMe. As you are limited by PCIe 3.0 x4 speeds. You'll get great IOPS. Which isn't important for large files. Sequential Read/Write is what matters.

Assuming you are building for capacity. As long as the RAID card can handle the speed in RAID 0/5/10. You may get the same results for less money doing a SATA SSD RAID. Since sequential transfer speed is more important than IOPS with large media files. I'd figure about eight SATA SSD would saturate the Thunderbolt 3 connection.

Be aware that eGPU tend to be a bit temperamental on Macs. It's not something I'd want on a media creation machine I'm trying to make a living with. You're talking about a lot of time and money for something which is not reliable. What you really need is a rackmount Mac Pro if you must use a Mac. Otherwise build a Threadripper workstation with 72 usable PCIe 4.0 lanes.

 

[james211]

Be aware that eGPU tend to be a bit temperamental on Macs. It's not something I'd want on a media creation machine I'm trying to make a living with. You're talking about a lot of time and money for something which is not reliable. What you really need is a rackmount Mac Pro if you must use a Mac.

I was under the same impression initially, however there are a lot of DIT's (technical name for my job) who are great success with eGPU's provided the GPU is an apple approved GPU.

My initial thought was exactly the same, basically the DIY method. I'm pretty good with modding things so I wouldn't see this being an issue.

I appreciate your response, you stated the facts rather than calling me out as an idiot who doesn't know all the facts.

 

[velocityg4]

I was under the same impression initially, however there are a lot of DIT's (technical name for my job) who are great success with eGPU's provided the GPU is an apple approved GPU.

My initial thought was exactly the same, basically the DIY method. I'm pretty good with modding things so I wouldn't see this being an issue.

I appreciate your response, you stated the facts rather than calling me out as an idiot who doesn't know all the facts.

You're welcome!

I know the eGPU can require some tweaking to get it to work right. Sometimes delving into Terminal. Which is daunting for the uninitiated. Thus my inclination against it for a production environment. Once you get it working right. It'll probably be fine. Although I'd be hesitant to perform OS upgrades or patches without a cloned boot drive. So, you have something to fall back on. If the OS update breaks something.

You can get loads more help with this on Macrumors.com. There's a lot of mac addicts there. Also checkout egpu.io.

As I understand it. The Apple approved option, Blackmagic, is non upgradeable. If you want something upgradeable. You'll want a Sonnet enclosure for the eGPU. Then you can toss in a Radeon Rx 5700xt. Rather than spending a lot more for last gen tech. Although the 5700's drivers aren't fully optimized yet. As far as I'm aware. Sonnet's a good company. I haven't used their eGPU. I've been using various cards and accelerators for Mac's from them since the 90's and never had cause to complain. There are other brands to consider. I like the idea of Sonnet due to their legacy of Mac upgrades.

DIY shouldn't be too difficult. If you're handy with some metal work. It's just time consuming.