Format external hard drive for both old and new macs

Your Seagate hard disk drive, with Mac OS Extended (HFS+) format, should be fine working with both the old and new Macs, regardless of their native operating system. It should be fine for general storage and use between computers.

You posted that the HDD is "older". How old is it?

If it's more than five or six years old, the potential for mechanical distress increases. You might consider running diagnostics to check the health of the drive. DriveDX from Binary Fruit is great for that and I believe they have a free trial available.

Yes, APFS was developed and optimized for SSDs, but it can also be used as the format for an HDD. There has been some anecdotal evidence that suggests that the use of APFS on HDD is less than spectacular in performance.

There may be several reasons the drive isn't working well with the MacBook. The use of the HFS+ format is not likely to be one of them.

Most likely is a bad cable or adapter. Try something of better quality. Try connecting to different ports on the MacBook

Is the Seagate drive a small 2.5" laptop class drive that pulls power from the computer port, or is it a desktop class 3.5" drive that has its own ac power adapter? If the former, its possibly not getting quite power it wants from the computer and so the connection drops. You can check in for that info. Option-click  > System Information > Hardware > USB then select the drive and check the "Current Available (mA)" and "Current Required (mA)".

cowabunga97 wrote:

I have a 2011 iMac running OS 10.12, and an m1 macbook running 13.2. I have an older Seagate external hard drive that uses usb A, and when I try to use it with the macbook (using usb A to thunderbolt adapter)

I'm guessing that you are referring to a USB-C to USB-A adapter that is using the USB signal on the MacBook's multi-purpose (USB, DisplayPort, Thunderbolt) ports – not the Thunderbolt one.

there's no problem transferring files from the Seagate to the computer, but it is extremely slow or doesn't work at all (Seagate spontaneously ejects) if I try to transfer files from the computer to the Seagate.

Which adapter are you using? The Apple one, or some other brand? If some other brand, is it rated for USB 3.0 or only for USB 2.0?

I wondered if it was the adapter, but then I read about how 10.12 and earlier uses Mac OS Extended format for external hard drives, and 10.13 and later uses APFS. The Seagate is indeed formatted with Mac OS Extended, as I had only been using it with my older iMac up to this point. So is the format the reason it won't work well with my macbook? And what can I do to rectify this? I would like to be able to use the Seagate with both my older iMac and newer macbook.

Current Macs have no problem working with drives formatted using HFS+. I would think that there might be some problem either with the old drive or with the adapter.

One other potential issue is that I read that APFS is meant for SSDs and does not work well with HDDs, and I believe my Seagate is an HDD.

The issue there is that APFS apparently does not try to control fragmentation as much as HFS+ does. With a SSD, the random access time penalty to jump from one part of the drive to another is very small. With a HDD, there is a need to physically move the read/write heads to a new track, then wait for the disk to spin in place under them.

I would be very suspicious of a ten year old HDD. I wouldn't hesitate to replace it if it were mine. Eight years is a magic number in HDD lifespans. About half will fail within eight years. Those that don't are living on borrowed time.

The Disk Utility First Aid routine is very limited in ability. it can correct some directory and catalog problems but it doesn't do diagnostics at all. You cannot rely on DU to rule out mechanical issues, and the new Mac may not be as fault resistant as the older Mac when it comes to communicating with external drives. The DriveDX app is a much more comprehensive diagnostic and will see and report issues in a clear report. I'd run that against the drive and see what it has to say.

As for cables vs adapters: I believe cables are a better choice if for no other reason than it reduces the potential number of items to troubleshoot should something go wrong. A single point of failure instead of two. The cable you linked earlier appears to be a reasonable replacement for your current cable+adapter situation.

Does your cable or adapter work well with another device? It's likely one of those. The drive format is fine though the age of its mechanical parts might be taking a toll.

A USB-C to USB 3.0 Micro B cable like the one you found would be a reasonable substitute for using the bundled cable with the Apple adapter. But I don’t think it will solve your problem because I suspect the problem is somewhere other than in the cabling you are using now.

To the best of my recollection, System (Report/Information) often has/had S.M.A’R.T. status for internal and Thunderbolt drives, but not so much for USB ones. If the Mac is not seeing that status, it might not give you any warning (aside from slowness and malfunctions) that a drive was failing.

If you have problems accessing the older backups on your Time Machine drive hold down the Option key when accessing the menu and select "Browse Other Backup Disks…":