David: Before finding out that Feedback Assistant, and your advice in general was really directed at beta versions of the OS, I carefully documented, per your suggestion, an “interesting” problem I have encountered, that may in the end be related to a fault in a basic chip design. It’s all I can think of. Is there a way of bringing this to the attention of Apple?
External disk spontaneously ejects… T2 chip problem?
This is a new problem that I have never encountered before. My most recent Mac, an iMac Pro was purchased 3/14/19. (3.2 GHz intel Xeon W, Mojave 10.14.6) I have not upgraded to Catalina (for reasons of legacy software), but have updated system versions as they were released. I have used an external disk for Time Machine backups. (OWC Mercury Elite Pro, using USB port on iMac, and USB 3.1 Gen 1 port on disk.) Backups worked flawlessly for almost a year.
As the disk was getting full, I purchased (on 2/20/20) another OWC Mercury Pro Elite disk and started a new Time Machine backup (using the same USB connection). After a few hundred gigs the backup stopped with a “Disk not ejected properly” message. I cycled the power on the disk, it remounted with no problems, but then ejected spontaneously after a few hundred gigs more. It finished the backup (about 1 TB) after another two or three power cycles on the disk. I left the system running for incremental backups, it would run about a day and then spontaneously eject. This pattern repeated itself thereafter.
I spent half an hour with a tech from OWC, who said they had seen this problem with Catalina, but never with Mojave. In the end he had no solution, but did offer to exchange the disk if I thought this necessary. (So far I have not taken him up on this.)
I posted a query on Tidbits Talk (“External disk spontaneously dismounting” Jose Alonso, June 10, 2020), and received several replies documenting the same “disk not properly ejected” messages, with different disks, different connections, and not related to Time Machine. However, the message that proved most useful pointed me to:
which led to:
this last intimated a possible problem with the T2 chip, suggesting that resetting the SMC might help. The procedure given was to power down the computer, unplug it, wait at least 15 seconds, plug it back in, wait about 5 seconds then power the computer back up.
Also note, my iMac is on all the time, it had not been rebooted in many weeks, probably not since the last power drop by PG&E in our area.
I followed the reset recipe, and had no “disk improperly ejected” messages for several weeks. Recently the messages started reappearing. I cycled the disk power, … the problem has recurred with a frequency of about once per day. This afternoon I repeated the power-down-SMC-reset process, it is probably too early to say but so far the problem has not reappeared.
As I say, I have never seen this problem before, so it must be related to either a subtle hardware problem, a modification (“update”?) of disk controllers spread across different disk vendors (it did not occur with the previous OWC drive), or some other new sensitivity.
I am a nuclear physicist, and have been involved with work at Berkeley Lab on radiation sensitivity of chips, specifically single-bit upsets (soft errors) caused by cosmic rays. Any chance this may be behind this problem?