External drives · bench notes · ADR-2025-2869
The Listing Was There. Nothing Behind It Was.
Two Macs, an iMac and a MacBook, and the drive had stopped behaving properly on either of them. It does not automatically mount when plugged into my iMac or Macbook
, she wrote, so she had got into the habit of mounting it by hand — which worked, after a fashion. Once mounted, the folders appear but will not open
. Names on the screen, dates beside them, and nothing whatever when she double-clicked one. She had not run a repair tool over it and had not reformatted anything, which is a large part of why this entry ends the way it does.
Same story on yours? Tell us what it does — the look is free.
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What failed, and why.
A file system keeps two things apart. One is the index: the names, the dates, and the note of where each file physically lies. The other is the file itself, out on the platters somewhere else entirely. When folders list but will not open, the index has been read and the contents behind it have not — so the volume is neither empty nor blank, it is failing at the second step. The manual mounting says the same thing more quietly. A Mac puts a healthy volume up by itself in a second or two; when it will not, something underneath is answering too slowly for the automatic process to wait on. And every further double-click is another round of retries against a mechanism that has already shown it cannot be relied upon.
What the bench did with it.
The order of the job →| Equipment used | Its work on this job | The reason for it |
|---|---|---|
| DeepSpar Disk Imager 4 | Read behaviour profiled zone by zone, then the copy taken with retries held short | Heads mapped first, then one platter side to a pass, with every reset, every timeout and the power itself kept under our own control |
| DeepSpar USB Imager | The first pass ran through the caddy's own USB board, with no Mac in the path at all | Reads through the caddy's own USB board rather than round it, and at the pace the bridge allows |
| UFS Explorer Professional Recovery | The Mac volume was parsed off the finished copy and the folder contents lifted out | Opens APFS, ReFS, XFS, ZFS and Btrfs when other software will not |
What the bench did with it.
Find out what the slowness is
Nothing was mounted, opened or double-clicked here; the drive was measured instead. Read timing was taken across the whole surface, zone by zone, and the pattern was plain enough: long stretches at full rate, then bands where one sector took hundreds of times as long to answer. That is what the automatic mount had been giving up on. It also explains why her folders listed at all, since the index sits in a region that still reads while a good deal of what it points at does not.
Take one copy, and keep the retries short
A drive in this state has a fixed budget of reads remaining, and repeated attempts spend it on the same few sectors. So the copy was taken once, behind a write blocker, with the number of attempts on any address fixed in advance and the slow bands set aside for a final sweep. Sound regions crossed at full rate. Nothing that had already answered was ever asked twice.
Open the folders here, not on the drive
Her folders were opened on the copy rather than on the drive, and the copy is the only place they were ever opened. The Mac volume unpicked cleanly, the tree stood up in the shape she had built it, and files were checked by being opened rather than by being counted. A count would have proved nothing useful here.
What went home.
Almost all of it is back. The tree went home on new media folder for folder, and every file was opened at this bench before it went. A short list did not survive: those lay in the bands that had refused throughout, and each of them is named in the report itself, with no percentage attached to any of it. The WD did not go back with the recovery. A drive that has once been unable to hand over what its own index points at has no business holding the second copy of anything.
Begin here if yours is doing the same thing.
Further portable-drive jobs, written up.
Yours doing something similar? Power it down first.
Prices are published and fixed. Memory cards and USB sticks are priced at £250 + VAT. A drive on its own comes to £300 + VAT. Anything holding a second disk, whether RAID, NAS or a server, opens at £500 + VAT. The first look costs nothing, and the figure that follows is fixed and in writing before a penny is charged. Switch it off and post it in. Most jobs carry no fee where no files return.