second NVMe enclosure not detected when first one is connected?

IllRepute wrote:

This is so bizarre. I have two TB4/USB4 NVME enclosures with the ASM2464 chipset. Both my M1 Mac Mini and my M1 MacBook Air can mount both drives concurrently, however my GF’s M2 MacBook Air will only mount the first connected drive. System info shows that both enclosures are connected fine via Thunderbolt, it’s just the second drive that won’t mount.

Are these drives actually using the Thunderbolt protocol, or could they be using the USB protocol? USB-C is not necessarily Thunderbolt.....USB-C is a connector style. Most consumer drives will be using the USB protocol.

What is the exact make & model of these two drives?

Are the exact same cables & adapters being used?

If these are indeed Thunderbolt drives, then do they have multiple Thunderbolt ports to allow device chaining?

Are both of these drives showing up on the same Thunderbolt bus? If so, then try connecting one of them to the other side of the laptop.

Disconnect all other external devices. Connect only these two external drives directly to the laptop using a dedicated USB-C port for each one, best if the two drives are connected to different sides of the laptop (at least for testing purposes).

What file system is on these two drives?

What else is different between the two systems that can see the drives and the one that cannot see them both? Third party software can easily cause problems. Try booting into Safe Mode as long as you are not using any third party software to manage these external drives.

If you are using third party software to manage these drives, then make sure that software is up to date and actually compatible with the exat version of macOS being used. Also make sure macOS is fully up to date.

Power! Turns out the draw of power of each item on USB-C is such that having multiple devices connected that depend on the computer's power may prevent one device from working when more than one device is connected.

Furthermore, Energy Saver has an option to put hard drives to sleep when activated. If you turn this off, it may work better.

But you are better off getting enclosures that come with their AC power adapter than depending on computer power to connect to the Mac regardless. If you must use one that doesn't have AC power, get a USB-C hub that has its own power source other than the computer.

Doubt all you like, but as I say, a simple experience is save the frustration and get yourself an AC/DC powered Thunderbolt 3/4 hub. You could buy a wide variety of enclosures and spend a lot more money trying to find the exact enclosure that works, or just get something that avoids the most obvious problems I listed. It has been my experience that even a single LaCie Thunderbolt 3 drive on a MacBook Pro without an AC powered hub would not connect until I got myself a power pass through hub like

https://www.smklink.com/products/usb-c-multi-port-hub

GIven you have two, something like this might work better:

https://www.bhphotovideo.com/c/product/1673763-REG/sonnet_echo_hb5_t4_echo_5_thunderbolt_4.html

That seems very odd. How does the PCIe lane limit translate into the USB-C managing the buses of each hard drive? You would think it would be independent. Again an argument for trying a powered hub. It can manage the traffic independently of the USB-C bus on the computer, and hopefully also bypass the limit being imposed by the USB-C bus of the computer. As long the hub is not powered by the computer, it likely will work better.

This is so bizarre. I have two TB4/USB4 NVME enclosures with the ASM2464 chipset. Both my M1 Mac Mini and my M1 MacBook Air can mount both drives concurrently, however my GF’s M2 MacBook Air will only mount the first connected drive. System info shows that both enclosures are connected fine via Thunderbolt, it’s just the second drive that won’t mount.

What architecture or software changes were made that could cause this setup to work on M1 but not M2?

Yes, these are true TB4/USB4 enclosures with the ASMedia ASM2464PD chipset. They are Jeyi and Maiwo branded. Both show up in system report under the Thunderbolt/USB4 tab as 40Gb/s devices. The drives inside are both WD Black SN850X 2TB NVME. One is using the Jeyi TB4 cable and one is using the Apple TB4 cable. All firmware for the SSDs as well as the enclosure is current. MacOS is current. They are each connected to their own TB port on the computer, as they don’t have daisy chain capability, and thus each shows up on an independent bus in system report. No other devices are connected to the computer and no apps are running. They are both APFS and no software is needed or used to manage these drives.

Both sets drives/enclosures/cables work perfectly by themselves on the M2 and read/write at over 3000MB/s. Both sets work perfectly concurrently on my M1, and I can transfer 250Gb of files from one drive to the other in 3 mins, 30 seconds. Really nothing at all wrong with these devices.

The only issue is that when plugged into the M2, only the first connected drive shows up under “storage”. Both enclosures are concurrently detected under “Thunderbolt/USB4”. Swapping cables, etc, makes no difference. It’s always the same behavior, each component works perfectly on its own but the second chronologically plugged in drive never mounts. This is only occurring on the M2, M1 works exactly as expected.

The last suggestion of yours I could still try is safe mode, which I will check out this evening. Thanks.

Same problem on a M2 Mac. Not an issue on my intel Mac. However the ZikeDrive USB4 drives don't have that problem and they're faster