I have. Mac Mini M4 and an MacBook Air M4 and I have them connected with a Thunderbolt 4 cable via a thunderbolt bridge? 1.) Is this necessary to have it set up with a bridge? 2.) I am only getting blackmagic speeds of about 950MB/s and was expecting much higher speeds. This is what I would expect from a 10Gbps connection and not a 40. Any assistance would be appreciated.
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Speed of Thunderbolt bridge? M4 mini to m4 MacBook Air with TB4 cable.
- Thread starter ricknot
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On multiple uses I got also ~1000 MB/s, but last time I got nearly 2000 MB/s, I don’t know why. I will test the speed again later and give a feedback.
Are you sure your TB4 cable is good? Have you tested it with another device? or your bridge using another cable?
Also, IIRC, 40gbps is the duplex speed of TB and the max you can get in one direction is 20gbps.
Also, also, are you using built-in file sharing? Apple's SMB implementation is not exactly the greatest.
Also, IIRC, 40gbps is the duplex speed of TB and the max you can get in one direction is 20gbps.
Also, also, are you using built-in file sharing? Apple's SMB implementation is not exactly the greatest.
Up through Thunderbolt 4, it's a pure full duplex interface - there's dedicated signals for each direction. TB4 has 2x20G in and 2x20G out for a total of 40 Gbps in and 40 Gbps out.
Thunderbolt 5 retains the same number of signals (2 in, 2 out), but increases line rate to 40 Gbps, twice as fast as TB4. Thus, it's normally 80 in / 80 out. However it also adds a new mode where one of the input signals is turned around to become an output, meaning you get a total of 120 Gbps out and 40 Gbps in. This is mostly intended to support refreshing multiple high bandwidth displays (8K displays, or 4K @ 144 Hz) through one TB5 port.
okay at someones suggestion I have run iPerf3 on the two Macs in question and guess what? It shows a speed of 37gbps over the thunderbolt bridge. The Blackmagic test still shows around 900 MBps so what the hell is going on? It seems like there is some kind of added delay of a pretty good magnitude on the internal drives of the Macs. Is that possible?
Yeah, 37Gbps sounds about right for Thunderbolt 3, so the cabling seems good.
I could be wrong, but I think when you access the internal drive of the other Mac, you are essentially accessing it over a network (even though it's a Thunderbolt network). If so, then macOS is using the SMB network disk protocol. I've read that SMB is not very efficient, and that the macOS implementation is not very "good"(?). My guess is that the slowdown is caused by this 'network drive' access with SMB.
One could rule out SMB by using 'rsync' in Terminal. My understanding is that it uses its own (faster) protocol.
IMHO, 950 MBs is not bad a performance for a network-attached drive. One shouldn't expect 2800 or 3000 MBs like you could get with a Thunderbolt 3 or USB4 enclosure that's directly attached.
I could be wrong, but I think when you access the internal drive of the other Mac, you are essentially accessing it over a network (even though it's a Thunderbolt network). If so, then macOS is using the SMB network disk protocol. I've read that SMB is not very efficient, and that the macOS implementation is not very "good"(?). My guess is that the slowdown is caused by this 'network drive' access with SMB.
One could rule out SMB by using 'rsync' in Terminal. My understanding is that it uses its own (faster) protocol.
IMHO, 950 MBs is not bad a performance for a network-attached drive. One shouldn't expect 2800 or 3000 MBs like you could get with a Thunderbolt 3 or USB4 enclosure that's directly attached.