kernel panic 2-3 times per day, every day since Catalina 10.15.3

Dealing with Kernel Panics

Disconnect any third-party peripherals including any USB hubs. Use safe mode to isolate issues with your Mac - Apple Support then boot the computer into Safe Mode: Use safe mode to isolate issues with your Mac - Apple Support and Playing Safe- what does Safe mode do?. See Diagnosing problems- crash, freeze, panic, or spinning beach ball?, Don’t Panic! Understanding & Troubleshooting Kernel Panics in macOS, and How to fix kernel panics after installing OS X updates | MacIssues.

Kernel panics are indicative of possible hardware failure, so you should Check your Mac with hardware diagnostics or AHT. Read the kernel panic log: Mac OS X- How to log a kernel panic.

If you have no success figuring what is happening then you may need to examine the software you have running when the panics occur. Be sure it’s all current. If you must to resolve the problem erase the disk and reinstall macOS. Follow this outline to reset the computer to the factory-new state: Factory reset of your Mac - Apple Support.

Boot Into Safe Mode

1. If your Mac isn’t already shut down, then shut it down and wait at least 30 seconds before rebooting.
2. Immediately, at or before the chime, press and hold down the SHIFT key. 
3. Release the key after the Apple logo and progress bar appear.
4. Safe mode startup is much slower than normal startup, so be patient.
5. When the Login Screen appears enter your admin password. If you use automatic login, then this means you are in safe mode.

Please post the Kernel Panic logs so we can actually examine them. Please post several of them as it may help in the diagnosis.

To check for possible software issue you can also run EtreCheck with "Full Disk Access" and post the report here using the "Additional Text" icon which looks like a piece of paper.

EtreCheck is reporting that your hard drive is failing and it could very well be the source of your problems.

I am not familiar with "bearisdriving".

Your Console app doesn't have all the items it should have listed in the left pane unless this is new with Catalina. I haven't used Catalina too much so I cannot be sure. I've never seen a Kernel Panic in .json before, but I haven't used Catalina enough to see a Kernel Panic either. To run Console from the Terminal may require the use of the "open" command, but I'm not an expert on macOS software. The macOS command line does have a new "log" or "logs" command which can be used to view logs or to export them into a format readable by the Console app.

You can check the health of the hard drive by running DriveDX if you want to confirm what EtreCheck is reporting. Post the DriveDX report here using the "Additional Text' icon which looks like a piece of paper.

The internal hard drive looks good although the transfer rate listed is a bit low even for a slow Apple drive, but I've never really looked at those values except for assisting on these forums so I'm not sure what is considered normal. My guess is something else is affecting those numbers since it took a long time for the original EtreCheck report to run.

Have you run Disk Utility First Aid on the internal drive?

Since you have several external drives connected to this computer it is very likely one of those external drives is causing a problem especially since your original post mentions I/O subsystem and SCSI/USB. To make sure the computer itself is working fine you should disconnect all those external drives including any hubs to see if the problem occurs which would at least tell you the issue is with the Mac or macOS. Then you can test each drive individually.

If these external drives are connected to a hub, then I would suggest connecting the drives directly to the computer since the quality of many hubs is quite poor these days.

If these drives are connected directly to the computer, then try using a good powered USB3 hub with UASP support which may provide more power to the drives and also the hub will act as a buffer which may help make everything work more reliably.

ksaro1 wrote:

<DriveDX Report.log>

Initially DriveDX reported the external USB drives couldn't be scanned because they required a 3rd party driver, which I wasn't going to install just in order to diagnose a Mac OS issue, as obviously the OS doesn't require the drivers for a kernel panic.

However, when I then ran DriveDX to produce the attached report, DriveDX no longer shows the external USB drives? They are mounted and shown in Finder and Disk Utility. Odd.

To access the health information on the external drives requires a different type of communication than normal data transfers and unfortunately Apple does not have this support built into macOS so a special third party USB driver is necessary to allow the necessary communication to access an external drive's health information.

USB sticks cannot be tested since they do not have any built-in health checks.

Unfortunately even with this special USB driver there is no guarantee DriveDX will be able to communicate with the external drives since the manufacturers of the external drives do not always allow the necessary communication to pass through (usually limited by the USB controller on the external drive). There is no other way to check the health of the external drives from within macOS unless the manufacturer provides their own utilities to do so. In that case I would trust the DriveDX USB driver over the proprietary software provided by the drive manufacturer (especially when you have multiple brands of drives), but that is just me.

I do not blame you for not wanting to install extra software especially a third party driver. I also try to minimize what is installed on my own systems so I really do understand.

It is possible to boot from a Linux Live USB drive to attempt to check the health of the external drives if you don't want to install a USB driver on a Mac. I use this method a lot when working on other people's computers.

It id quite likely that the drive is failing. In any case, a 5400rpm hard drive is a terrible bottleneck that is preventing the iMac from performing properly. These 15 to 20 minutes to start up? They could be 30 seconds.

Get a SATA SSD and a USB3 case to put it in. It may cost maybe $50 or less. Install on this SSD and see your iMac perform as it always should have.

It is a shame that Apple sold these otherwise great machines with those dog slow drives.

The free version of SuperDuper! can do that, easily.

The main limitation vs the paid version is that the free version does not allow incremental backups. In this case you need to erase the SSD and clone everything, so the free version is all you need.

Full disclosure: I do have the paid version, and I am a satisfied customer.

It allows me to maintain up to date clones of my system, using the incremental option (that it calls "smart update"). Totally worth it for me. If my mac dies in an hour, I can just plug my external drive to a new mac, or a borrowed one, and I have everything up to date (up to the time I last updated the clone, of course).

Lots of people use Carbon Copy Cloner instead. It also has a great reputation. I don't know if it offers a free version.

ksaro1 wrote:

Also, it does seem a bit suspect that HDD errors on a drive other than the actual OS drive can crash the Mac. I've very rarely seen this on other computers and OS'es.

It is a bit odd when it is not the boot drive, but macOS does not handle drive errors very well anyway. Plus it is hard to say how the drive's USB controller is handling the errors.

If nothing else you've eliminated a weak point in your system before it got to the point where accessing data would have been difficult.

I've personally had issues with external USB3 drives connected directly to my Mac so I've had to resort to using a USB3 hub with all external drives which seems to buffer or filter the connection which has eliminated my external drive issues.

Disk First Aid only checks the integrity of the filesystem. Essentially, that is the logical organization of the data on the disk. The only time Disk First Aid could detect a hardware failure would be if the hardware failure directly affected a portion of the disk that contained the filesystem metadata.

You seem to have two different issues - kernel panics and slow hard drive read speeds. It is possible they are related. I don't know if you've ever run the system without said USB disk. The kernel panics do seem to be USB related. Unplug all external drives and use the system. The kernel panic involves the USB system, but it could be anywhere in the system. The external USB drive could be fine. Maybe it is the internal USB bus that is failing. These things aren't precise.

It is possible that removing the faulty USB device will improve your boot drive performance. If there are hardware problems, they could affect the entire system. You can run EtreCheck a few more times with no USB devices plugged in to check. 27 MB/s is almost stopped. So unless it gets much, much better on subsequent runs, then the hard drive is probably dead. Or perhaps some other internal component is failing, which is affecting both the hard drive and the USB drives and all the physical disks are fine. Isn't debugging fun!

HWTech wrote:

The internal hard drive looks good although the transfer rate listed is a bit low even for a slow Apple drive, but I've never really looked at those values except for assisting on these forums so I'm not sure what is considered normal. My guess is something else is affecting those numbers since it took a long time for the original EtreCheck report to run.

EtreCheck considers anything under 30 MB/s to be in "OMG failing!" category. 30-40 is "real bad". Anything over 40 is considered "good". But remember that EtreCheck is extremely conservative on these things. A 2.5" notebook HD should do at least 50-60. A 3.5" desktop drive should be 80-100. An upgraded SATA SSD should be 450. OEM SSDs range from 750-3000. I've been seeing a number of upgraded SSDs in the 250 range, but I haven't added any warnings about those yet.

EtreCheck also has a filesystem check. This can be useful for detecting interference from things like antivirus, drop-box, or cloud-back-du-jour. It should take 30 seconds. If EtreCheck has to force-terminate the test after 2 minutes, that's bad.

The overall runtime, is more mysterious. I think this is a good measure of what kind of performance the user is really experiencing. But it is a result of many system-level issues. A modern machine with an SSD should run in 3 minutes. A decent machine with a mechanical hard drive should take 4-5. If there are external disks connected, it will take longer. EtreCheck detects that and tries to add a fudge-factor.

EtreCheck also lists the nominal I/O for the boot device. If that is very high, then the test results should be correspondingly less. I haven't decided if I should add the I/O for other devices too.

Also, EtreCheck is a snapshot. A subsequent report might be fine. Such is the nature of "performance" tests on a UNIX system.

I will Apple would just get rid of Disk First Aid. It hasn't done anything except confuse people for the past decade.