USB stick unreadable on older machines

[DanL]

So I loaded up a SanDisk Ultra USB stick with some stuff, using my M1 iMac on Monterey. Plugged that stick into older Macs (El Capitan), and NO ICON SHOWS UP ON THEIR DESKTOPS. Yes, Finder is set to allow that to happen. It also doesn't show up in Devices on the Finders. Now, if I go to Disk Utility, I see the stick is logged there. The machine knows about it! Partition map is GUID, which should be fine. The stick has all permissions enabled. What am I missing??? Why can't I read this stick on other machines?

Well, OK, I realize that the stick is recognized, but not mounting on my older machines. In Disk Utility, the "Mount" button for that stick is greyed out. How do I get it mounted, and why shouldn't I be able to do so? Is this some funny formatting issue?

 

[Applescrumpy]

Is the USB stick formatted as APFS? If so El Capitan won’t recognise it. You could erase and reformat the stick in HFS+ Format and copy your files back to it from your M1 system.

 

[DanL]

Thank you. That was exactly right. I figured that out myself. The incompatability of APFS with older systems is annoying. I gather the main value of APFS is speed, and indeed that seemed to be the case. It took half as long to load up my stick on AFPS as it did with OS X Extended (partitions). But it is curious that Disk Utility knows the stick is there, but the stick won't mount.

 

[TonyAguila]

So I loaded up a SanDisk Ultra USB stick with some stuff, using my M1 iMac on Monterey. Plugged that stick into older Macs (El Capitan), and NO ICON SHOWS UP ON THEIR DESKTOPS. Yes, Finder is set to allow that to happen. It also doesn't show up in Devices on the Finders. Now, if I go to Disk Utility, I see the stick is logged there. The machine knows about it! Partition map is GUID, which should be fine. The stick has all permissions enabled. What am I missing??? Why can't I read this stick on other machines?

Well, OK, I realize that the stick is recognized, but not mounting on my older machines. In Disk Utility, the "Mount" button for that stick is greyed out. How do I get it mounted, and why shouldn't I be able to do so? Is this some funny formatting issue?

Why don’t you first copy all the contents of the USB stick to your M1 iMac and then connect it to your older Mac. If you say that it shows up in Disk Utility but will not mount, try to erase it and use the format that the older Mac can read and write to, probably HFS+. Eject.

(APFS is not necessary on data disks, only on systems disks. But try to adopt APFS whenever possible, even for your Time Machine drives. The move to SSDs is one of the main reason for changing over to APFS.)

Now connect it to the M1 iMac, copy the old data to it, and then walk it back over to the old Mac. Make sense?

 

[DanL]

Well, this isn't a matter of moving data from one machine to another. That's trivial. I'm using a stick as a convenient archive (don't worry, I have vastly more secure archives), so it's really a matter of my archive being readable on different machines. That's correct that SSDs are the reason for the move to APFS, and it's mainly about speed, which is what I easily saw.

 

[TonyAguila]

Well, this isn't a matter of moving data from one machine to another. That's trivial. I'm using a stick as a convenient archive (don't worry, I have vastly more secure archives), so it's really a matter of my archive being readable on different machines. That's correct that SSDs are the reason for the move to APFS, and it's mainly about speed, which is what I easily saw.

In any case, by formatting the thumb drive on the older machine, it should be readable on both Macs. You can keep the USB drive that way forever, making sure that you have information on it that are accessible to both Macs.

 

[DanL]

That's true. I could have just formatted on the older machine.But now that I know how I need it formatted,I can do it that way anywhere.

 

[TonyAguila]

That's true. I could have just formatted on the older machine.But now that I know how I need it formatted,I can do it that way anywhere.

Suggesting that you do it on the older Mac is just to ensure that it is readable by your least common denominator, which in this case is the older Mac.

After thinking more about it, though, you should probably format it as ExFat, in case you decide to switch over to a Windows PC in future. Then all three machines will be able to read and write to it.