Six Lessons Learned from Dealing with an iMac's Dead SSD

A post was merged into an existing topic: Your Mac Can No Longer Listen for Aliens, but It Could Help Cure COVID-19

That’s exactly what I did, and apart from slow boot and shutdown times, it seems to be working perfectly.

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I wonder if you could just delete all of its partitions, so there’s nothing to mount.

But I suspect that would end up causing the Finder and/or Disk Utility to present its “would you like to format a new drive” dialog every time you log in.

I wonder if there may be some other option to make the system ignore the drive.

A post was split to a new topic: Thoughts about buying a new iMac now?

The “Damaged Installer” results from an expired certificate. It may not always be an option to download a new installer. One solution is to change the date on your Mac to the date that’s on the installer. Get Info on the version of Install macOS xxx and look at the Modified Date. Set the System Date to that date. In Tools select Terminal and in Terminal firstly enter date and you will get the current time and date looking like this: Sat 2 Nov 2019 12:48:47 AEDT. To change it to 14 June 2019 at 12:24, the date I downloaded my last version of Mojave, you would enter: date 061212232019, then return to the Installer and it will work. I have used this trick to install old systems like El Capitan on old hardware and it is reliable.

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This isn’t all of the problem.

As @adam pointed out above, I downloaded a fresh Mojave installer from Apple just the other day and while it ran from my internal SSD boot volume, it refused to launch from an external HDD and instead gave me the usual damaged installer error. This is not just an expired certificate / date issue. There’s obviously more to it.

I’ve been pondering this too, but as far as I can imagine, the only way is a physical disconnection. And if you’re going in, you may as well replace the bad drive.

Just a few weeks after I bought my beloved 9600 Mac it was announced that the much anticipated, soon to be released OS X would only run on Intel Macs. Because it ran on RISC chips, for years I was shut out of upgrades and new applications. This became an even bigger bummer when soon after prices on all RISC Macs began to drop dramatically. As good a machine as it was, and it still has a place of honor near my desk, it became almost obsolete shortly after its birth. Although my very ancient MacBook Pro has been slowly but steadily manifesting signs of imminent death and its OS hasn’t been upgradable for years, I’ve been holding out for an A series replacement. My husband is hanging on with his MacBook Pro for the same reasons.

My advice is to stick it out unless you cannot avoid waiting. If you don’t like the A series Macs when they are released, it’s likely you’ll be able to get a better price on a current model.

Samsung literature for the T5 says, “Even when using USB 3.0 connections, T5 may not perform well if your system does not support UASP (USB Attached SCSI Protocol). Please make sure that your system supports UASP.”

I’m reasonably confident that my 2015 MacBook does not support UASP (since I can find no mention of UASP or SCSI in the USB portion of the System Report). How much “not perform well” am I likely to see? (Note that I would be buying a T5 disk for a Macintosh to be named at a later date, but using it with the MacBook until that later date.) Thanks.

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Yes, deleting the whole drive might work, and I’ve found a couple of web pages which give instructions on that. The fstab method unmounts the drive at some stage in the boot process but earlier in the process, the drive mounts. I think that’s where the problem occurs when updating the operating system (and sometimes when doing a security update). I think that the request to format the drive would probably come later in the boot process but I can’t be sure of that. I’ll need to think it through - it might be safer to open up the iMac and take out the HDD.

There’s never a right time to buy a new computer, other than when you need one. The fault with mine is not down to Apple (other than a poor choice of supplier) - it’s the Seagate 3.0GB drive which is known to be prone to failure. If it’s any help, I will definitely buy another iMac after this one (it replaced the previous generation of iMac 24 inch) but the design (at least on the exterior) hasn’t changed in over ten years and it must be nearly time for a redesign.

I also installed an SSD kit a year ago in my 2014 27" iMac 5K. Prior to that I used a Samsung T5 as my boot drive for about six months and things felt faster, but nothing compared to what I’m realizing now with the internal SSD.

There are times where I crave a faster iMac, but Python, shell scripts, and Affinity Designer are just fine with the old gal.

I’m lucky to also use a 13" MacBook Pro from work and use Jump Desktop to connect to it from the iMac since I run Windows via Parallels Desktop sometimes.

I honestly feel my iMac has much more value than what I would get if I sold it. The display is pretty cool. I also use Parallels Tools with Switch Resolution in the menu bar and sometimes take advantage of the full 5K when my eyesight is doing well.

By the way, I’m using an older 2010 iMac 27" in Target Display Mode as my second display and that’s a nice setup. :slight_smile:

I have never seen this mentioned there either, despite using some of the latest USB3 docks that I know offer support for UASP.

I have been told that in order to really check you have to look under Software > Extensions and check which kernel extension is actually loaded, IOUSBAttachedSCSI or IOUSBMasStorageDriver. If the former is loaded you are using it, if only the latter is loaded you are defaulting back to the old USB MSC. I have only seen the latter on this 2013 MBP so I’m assuming its USB3 is simply too old to support it.

Adam, I also thank you for the detailed write up. Articles like this (and all the comments) are one of the primary reasons I subscribe to Tidbits. And I agree with Doug Hogg – this kept me riveted in my seat to the end.
Some of my interest was generated by trying to update my 2013 MacBook Air to High Sierra. (yeah - I don’t keep up with all the new stuff :slight_smile: I was forced into an upgrade after installing a new application which could not run under Sierra. And the Mac App Store wasn’t helpful as it was forcing me to jump straight to Catalina. I did not want that because of some 32-bit apps that would be left behind.

It was quite an effort to find a link to the correct Apple installer. Just wish I’d seen Roland Mansson’s post with all the handy-dandy links right there. Gotta keep a copy of that one! Will likely move on to Mojave now that he has provided the article with its link to the installer.

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A quick web search finds this Apple discussion thread from 2014. The procedure described is:

  • Run the ioreg command to get the entire USB device tree, capturing its output to a file
  • Look for lines with devices of class IOUSBDevice and IOUSBAttachedSCSI. These are your UASP devices
  • Non-UASP storage devices will be of the IOUSBMassStorageClass

(The original version of this post mentioned an iousb command. That was a typo. Sorry.)

Thanks, @Simon. I got all excited because IOUSBAttachedSCSI was listed under extensions, then I reread your post and checked if it was loaded. It was not. I don’t suppose there is a way to tell the Mac to load IOUSBAttachedSCSI rather than IOUSBMasStorageDriver (which was listed as loaded)?

Thanks, @Shamino. I thought I was smart enough to do this, but I wasn’t. Terminal disavowed all knowledge of an iousb and I didn’t know where else to run it. Do you have a hint for me? (It probably doesn’t matter, since I assume the Software > Extensions result is conclusive, but I like to learn—even though I expect I’ll promptly forget what I learned.)

And another question, for anyone. After getting a System Report from About This Mac, clicking on Software > Extensions, and locating IOUSBAttachedSCSI, I thought to myself, “I’ll print this so I’ll have it later.” But in the Print dialog box available from System Information, I could find no way to print the selection or choose anything other than a page range for printing. Since the report was 102 pages long, it seemed like it would be tedious to find what I wanted, and I gave up. Did I miss some easy way to print just the IOUSBAttachedSCSI section (or any other section or group of sections)?

Also, repeating a question from my earlier post, how much of a performance hit would I suffer by using the Samsung T5 disk without IOUSBAttachedSCSI?

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Na, it wil load the kext if it can do it. If it isn’t loaded either the Mac or the bridge or the disk doesn’t support it (the former being the most likely).

The tip @Shamino gave you is just the command line equivalent. Its output is what Sys Profiler is displaying for you in a GUI. If you want to use the CLI, you have to do it using the command (I think he made a typo here)
which will dump a whole bunch of stuff so most people usually send it to file as in
ioreg > ~/Desktop/ioreg.txt.
However, that’s a huge can of worms so it’s probably easiest to narrow down using something like
ioreg | grep -i iousb
ioreg | grep -i iousb > ~/Desktop/ioreg.txt
if you prefer a text file as output.
That should contain only the relevant parts of the output. You will see that MassStorageDriver shows up instead of USBAttachedSCSI, like what you got from Sys Profiler. If your (or my) Mac supported it, we’d be seeing the other kext listed because that gets loaded for a UASP connection.

To answer your final question, when using UASP with an SSD instead of MSC you should see considerable read/write improvements, but of course you’ll always be limited to below the SATA3 bandwidth of 6 Gbps (which is why Gen2 can still make sense over Gen1 when using USB3 bridges).

By the way, is anybody seeing arrows at the top of this post indicating it was a direct reply to @Will_M? Or does anybody else see any indication at @Will_M’s post that it was replied to below? There used to be such indication on this board, but now at least sporadically, I’m not seeing them on some posts. Is this just me or is it some kind of bug in the latest Discourse version Adam has applied?

Sorry. Typo. The command is ioreg. I’ll have to go edit my post now…

As @Simon wrote, the system profiler shows you the same output. But when you run it from a command line, you can redirect the output to a text file:

cd ~/Destkop
ioreg > foo.txt

Then you can load the file into your favorite text editor or word processor and use its features to search for keywords like IOUSBAttachedSCSI

It appears that those back-arrow links only appear when all of the following conditions exist:

  • The post does not immediately follow the one it is in reply to
  • The post does not quote any text from the post it is in reply to

Bug or feature? That answer is beyond my pay grade. :slight_smile:


I’ve been confused about this as well. Weather it’s a bug or not, maybe Discourse should consider upgrading it.