It used to appear in the Finder and now it does not. Tried on a Windows PC as well, and nothing there either. Several years of backups on it. That second test was worth doing, because it removes half the possible explanations in one go. A drive missing on a Mac can be a formatting question — a Windows-formatted volume does not mount cleanly on macOS and an Apple-formatted one is invisible to Windows. A drive missing on both is a different animal. Neither machine is getting far enough to have an opinion about the file system, which means the drive is not presenting itself at all. That points at firmware, at the board, or at the mechanism, and it is answered by reading the drive directly on equipment that talks to it below the level either computer works at.
| Media | External backup hard drive holding several years of backups. No longer appears in the Mac's Finder or on a Windows PC. |
| Reported situation | External backup drive · stopped appearing in the Mac's Finder · also not seen on a Windows PC · several years of backups on it · recovery sought. |
| Fault class | Firmware, board or mechanical fault preventing the drive from presenting itself, which is why neither operating system sees it. The platter data is normally intact and is reached by reading the drive directly on equipment that addresses its service area. |
| Equipment used | Taken from its enclosure and read on PC-3000 UDMA through a hardware write-blocker, with power behaviour, the firmware and service area, the board and the mechanism all assessed one at a time · the fault dealt with according to what it was — service-area repair, board repair carried out with this drive's own ROM, or head or motor work under laminar flow in filtered air · imaged on DeepSpar, the backups located and validated in R-Studio. |
Two operating systems agreeing is useful evidence. macOS and Windows disagree about a great many things — file systems, partition schemes, whether a volume is worth mounting at all — but they agree completely about whether a device has announced itself. Both saw nothing, so the drive never got as far as saying what it was.
Announcing itself is the last step in a sequence the drive performs on its own. Spin up. Calibrate the heads. Read the firmware out of the service area, a reserved region of the platters no operating system ever touches. Build the translation between logical addresses and physical locations. Then, and only then, report a model and a capacity. Fail anywhere in that chain and the result is identical from outside: nothing.
Backup drives fail in a particular pattern that is worth naming. They spend most of their life powered down, come alive once a week or once a month, write hard for an hour, and go back to sleep. That duty cycle is unkind to bearings and unkind to heads, and it means the failure often shows up on the day you needed the backup, having been developing quietly for a year.
There is a wider point that goes with several years of backups on a single external drive: that arrangement is a copy, not a backup strategy. One copy in one place fails as a unit, and it fails at the worst possible moment. Two copies, one of them somewhere else, is the difference between an inconvenience and this phone call.
It came out of its enclosure so the drive could be addressed directly rather than through a bridge chip that mediates everything. It was read on PC-3000 UDMA through a hardware write-blocker, with power behaviour, the firmware and service area, the board and the mechanism each assessed separately rather than lumped together as not detected. The fault was then dealt with according to what it was — service-area repair where the firmware modules had gone, board repair carried out with this drive's own ROM where the electronics were at fault, head or motor work under laminar flow in filtered air had the mechanism failed. Once it presented itself, it was imaged on DeepSpar and the backup sets located and validated in R-Studio.
Read directly, the fault addressed, and several years of backups recovered onto fresh media. Assessment free, and one fixed written figure with VAT in it before any chargeable work. Which band applied followed from the fault: firmware and imaging work is logical and runs under no fix, no fee, while anything requiring the casing to be opened takes half the quote before that stage with the balance owed only on success. The advice that went back with the data was short. Two copies, one of them not in the same building, and test one of them occasionally by opening a file rather than by trusting a green tick.
You have already done the useful test, so stop testing. Trying a third and fourth machine adds nothing, because two different operating systems failing to see the same device has already told you the drive is not presenting itself. Do not accept any offer to initialise or format it — Windows in particular will suggest that, and it writes over the structures a recovery reads. Do not run Disk Utility's First Aid at it either. If it is making any noise at all, unplug it and stop completely, because that changes the fault class to mechanical and every further attempt costs data. Send the bare drive and say plainly what it was used for, since backup software leaves patterns that make locating the sets a good deal quicker.
Each file below comes from a genuine enquiry taken from households and firms across Aberdeen, Aberdeenshire and the wider north-east, anonymised so nobody can be identified. Each one sets out how the fault was reasoned through, what was done about it, and which equipment did the work.
No warning means no long decline, and no long decline usually means the data is all still there behind whatever stopped the drive presenting itself
Appearing in Device Manager only proves something is plugged in — the clicking is the mechanism failing, and every retry costs data
A computer that hangs the moment the drive is plugged in is waiting for answers the drive cannot give — and waiting is doing damage
Assessment is free and takes 2 working days at most once it lands, the figure is fixed in writing, and logical work carries no fix no fee. Begin online, or lift the phone.