Well, this is frustrating. It seems that there a variety of confounding variables.
I have seen this behavior for months and not just on Catalina. I have two external USB drives that periodically but only briefly lose connection. I see the system “ejected” error on the screen yet the drives remain visible and working. All of my equipment is protected by a UPS. I wondered if the UPS can’t respond quickly enough to a very short period power drop.
Are you guys absolutely sure you’re not suffering from something like brief voltage sags?
I have never seen such a disconnect before and I have several disks attached externally both at home and at work using different types of powered SATA-USB docks (Mojave, MBP, drive sleep enabled).
In my case, the brief voltage sags would need to correspond 1-to-1 with sleep, so I don’t think so.
My external volumes are not mounted for hours on end; I mount them when I have a reason and dismount them when I’m finished with them. I experienced the problem on the rare occasions when I was called away while a volume was mounted. As such, I have a small sample size (maybe eight events total), but my recollection is that I got the system error each time the MacBook went to sleep and I have not gotten the error when the MacBook has not gone to sleep.
Got it, @Will_M. I missed the sleep part. When hooked up to my external drives my MBP never sleeps the system, only external drives. At least it is set to do that, can’t say I’m sure it actually does.
I believe macOS still performs a lot of nightly cleanup tasks at ~ 02:00 local time (for instance). I know I have a cron job that performs a sync on a critical folder tree in the middle of the night as well. The OS is supposed to be smart enough to perform those jobs while “sleeping.”
I have three external volumes (2 x HDD, one SSD) in an OWC ThunderBay (4 bay, Thunderbolt 3). Unfortunately, it’s a very early model with an incompatibility with the Samsung EVO 860 SSD, and occasionally, the system crashes overnight.
Since 10.15.4, however, the system will crash overnight without any reference to that drive as long as any external drive is spun up. I’ve started unmounting all three volumes before sleeping the system for night. That fixes the crash issue, but I’m not certain how the thermal or mechanical stresses of spinning down and up the next morning compare with spinning overnight for the HDDs, in particular, the ~ 4.5-year old Toshiba 2 Tbyte drive.
OWC has documented a hang in large writes to external drives in 10.15.4, and verified that it is fixed in 10.15.5 beta 3: https://blog.macsales.com/60773-why-is-my-mac-hanging-when-copying-files-after-upgrading-to-macos-catalina-10-15-4/ .
Funny that you should mention this! I’ve been having an issue with an external drive (USB), connected to my iMac (27-inch, Late 2013), currently running Catalina 10.15.4. I use Carbon Copy Cloner to create a (clone) bootable backup of my primary HD each night.
I cannot, for the life of me, remember exactly when I upgraded to Catalina. Beginning in January, my nightly Carbon Copy Cloner task would OCCASIONALLY fail with the following message:
“The destination volume is present, but could not be mounted”
Disk Utility would display the BOOT volume, but grayed out … the DATA volume displayed normally, but nothing would mount. Power-cycling the external HD and rebooting the iMac brought everything back to normal and the backup would work fine for anywhere from 4 to 10 days … then it would fail again. A few times, I would remember to check to see if both the BOOT and DATA volumes appeared to be online … if not, I’d power-cycle and reboot.
FYI … I’ve replaced the power “brick” for the external HD, USB cable, changed USB ports, and finally changed the external HD with brand new one. Still sporadically happens …
Yesterday, my father (age 87) contacted me because the external drive I got him for TM backups several months ago appeared to have self-disconnected (with the same on-screen warning) around 2am. The drive is connected to his 2018 iMac via USB 3, and on battery-backed power. I looked at his logs and found nothing amiss. The drive checked out okay this morning, and seems to be working again.
I just noticed this discussion and wanted to add one more voice to the chorus.
And he is running Catalina (current as of yesterday).
I have had random disconnects of USB external drives, connected to both MBAir and iMac, with both High Sierra and Mojave. I believe these always occurred with drives connected via Thunderbolt docks. I never found a common denominator, but did not look hard, writing it off as inconvenience. Never any data corruption.
Looks like I have something to add to this post.
I just experienced two external disk drive disconnects with a new USB-C OWC Envoy Pro 1 TB device, within a two week period. I have a Mac mini 2018 that runs 24/7 and all energy settings are set accordingly, and no disks go to sleep, only the display. I also use a very good UPS and therefore any power related issues should be ruled out, plus when the drive disconnect there was no power interruption or surge. I purchased the Mac mini with only 500 GB storage, due to the high cost of going with the 1 TB option, but I kept running out of disk space very fast. I already had moved my Photo Library to an external drive and still I kept running out of space. I wanted a fast external Thunderbolt 3 drive, to migrate my home directory to it and was looking at the OWC Thunderblade, but their site listed it as being incompatible with the Mac mini 2018? I had a chat with a sales rep at MacSales and was told there is a bug in this Mac mini that causes the Thunderbolt drive to disconnect periodically. The only workaround would be to also purchase their external Thunderbolt 3 Dock, but this would have brought the cost way higher than I was looking to spend. I was recommend the USB-C Envoy Pro instead, since it did not suffer from this issue.
I contacted their tech support via chat, and they wanted me to run Disk First Aid, try another port and cable, or even backup the drive and reformat. They had not received any reports of disconnects with this drive. I ran the file system check last night and it found no issues and I will now have to wait and see if it disconnects again.
My Time Machine backup is and external USB 3 drive and I also have a Drobo 5D connected via the Apple Thunderbolt adapter. These drives never disconnect by themselves.
My previous 2012 Mac mini also ran 24/7 and is still in use running Linux Debian with the POXMOX Virtual Environment (actually I have three in a cluster configuration). One of those old 2012 Mac minis used an external USB 3 disk drive as its startup disk for many years and never ever did I experience a sudden disconnect.
My conclusion, there is an issue with this 2018 Mac mini, that may be starting to surface only now. Thunderbolt connection issues are nothing new, the v 3 Thunderbolt does have more bugs than any previous versions as seen by some of the updates that addressed these issues.
So if we know it’s not just Catalina (but also at least Mojave), we know it happens regardless of disk sleep settings, and we know it’s not a power issue, is it possible it only affects Macs of certain generations? Has anybody been experiencing this issue on an older Mac? I’m not seeing it on my 2013 MBP, but @mlooss reported the issue on an 2018 Mac mini. Anything in between?
I was seeing it occasionally on my 2012 MBP on Mojave before I took it out of regular service.
I see it occasionally on a 2014 Mac Mini running Sierra. It’s a media server and I haven’t seen the need to upgrade it to a newer OS yet. Thankfully when it happens it’s always the TM disk and not the the external where I store all of my media files.
Thank you, Gentlemen. I guess there goes that theory.
MacBookPro 2017 (Mojave), but I’m connected to an OWC USB-C Dock, so that could be a co-factor for me.
A followup to update my experience.
The outputs on either the wall checked out ok. I opened the outlet on my side and all wires were intact. (whew! I had installed new outlets and switches (80 in total) after the whole interior was repainted.) I used my outlet test device and both sides were good.
I got one dropout shortly after and immediately wiggled the dual lamp timer in the opposite outlet. The lamps flickered as it was trying to light them. I removed the timer. No more dropouts so far.
If this is the case, then the cause may be dirty power.
Look for a high quality power strip that includes a noise filter in addition to whatever surge suppression might be present. Make sure your computer and all its peripherals are plugged in to this strip. That might be sufficient.
The latest Catalina update claims “Resolve a bug where certain USB mice and trackpads may lose connection”. I wonder if this is related to the problems discussed in this thread.
I seldom see the Ejected Improperly repetitive error on every external drive. Once in a rare while it shows up but usually when I am moving the machine and the drives from one place to another.
I would say it was fixed. I closed the bug report.
They also fixed the bug that detected the iCloud Photo Daemons as if an app was still running and would not restart until the user quit the app, except the Photos app was already quit. The daemons always are running if I have iCloud Photos syncing.
The average user would not now how to start the utilities to force quit the background processes. Restart now safely quits the daemons.
I love it when I am the first (or maybe only user) to report a bug and they actually fix it!