A Mac that recognises a drive as a disc but will not mount it in the Finder has a filesystem fault, and the problem is not to do with the physical hardware. The Mac can see the disc, so the drive is powering and reporting, and what stops it opening is that its filesystem, the structure the Finder mounts, has become damaged, so all that needs to happen is to image it read-only and then rebuild the filesystem rather than format it. That it appears in the settings but not in the Finder indicates that the fault is within the volume itself and not the drive, and that the files are sitting behind the damaged structure, so they are recovered by rebuilding it. His 1TB external "has stopped responding when plugged into my computer"; it is "recognized as a disc" in settings but "does not appear in the finder window". A drive that is seen but not mounting has a filesystem fault, and it is imaged read-only and rebuilt, never formatted. The filesystem is rebuilt from a read-only image.
| Media | A 1TB external drive that a Mac recognises as a disc in settings, but which cannot be mounted in the Finder window. |
| Reported situation | 1TB external drive · stopped responding · recognised as a disc in computer settings · does not appear in the Finder · recovery needed. |
| Fault class | A filesystem failure, where the disc is recognised so the drive is powering and reporting, but its filesystem is damaged so the volume won't mount. The data itself remains untouched behind the broken filesystem, and it can be reached by imaging the drive read-only and then rebuilding the filesystem, rather than formatting the disc. |
| Equipment used | The drive was read on PC-3000 UDMA while connected through a hardware write-blocker, and confirmed to power and report at the disc level · It was then imaged read-only on DeepSpar so that nothing could be written to it · The Mac filesystem (HFS+ or APFS) was parsed in R-Studio, allowing the directory and volume structure to be rebuilt from the image, and the data was located and validated onto fresh media. |
Seen as a disc but not mounting indicates a filesystem fault. The fact that the Mac sees the drive as a disc but the Finder won't show it also points to a filesystem fault, because being seen as a disc means the drive is powered and reporting correctly at the hardware level, so it is working as a device. What prevents the Finder from mounting it is the filesystem, the structure that organises the files, which has become damaged. Therefore the problem lies in the volume and not in the hardware, as the drive is there and visible, but its filesystem cannot be mounted, and that is why the Finder appears empty, rather than because his data has disappeared. His data is behind that damaged structure and is reached by rebuilding it.
Seen in settings but not in the Finder identifies where the fault lies. The reason it appears in the settings and not in the Finder window is exactly the pattern of a filesystem failure, because the settings show the discs that the hardware reports, while the Finder displays only volumes it can mount, so a disc that is listed in settings but not mounted is one where the hardware is fine and the filesystem is not. As such his own observation places the fault precisely, as the drive itself is fine as a device but the volume on it is not, and it is the volume that gets rebuilt. His data is reached by repairing the structure that the Finder could not mount.
The drive is imaged read-only and rebuilt, and it is never formatted. Because the failure lies within the filesystem, the drive is imaged read-only and it is the filesystem that is rebuilt, with the drive copied without anything being written to it. The directory and volume structures are built up again from the image and then the files are recovered, so the data can be retrieved without touching the drive. It is also never formatted, as formatting (which a Mac may suggest if a volume cannot be mounted) writes a new, blank filesystem structure over your existing data. Rebuilding the filesystem is how data is retrieved from a drive that is seen but not mounted. The free diagnostic establishes the fault before you owe any money.
Typically the prognosis is good here, as the drive itself is sound. Where the disc has been recognised but the filesystem is the fault over sound storage, which is the usual case, rebuilding the filesystem recovers the data well and often in full. If there is a hardware fault behind it as well, that gets dealt with first, and then the outcome depends on the platters. Which of these applies is established at assessment by reading the drive, and the recoverable extent is confirmed before you decide, with the data usually recovered where the storage was sound.
The disk was read through a hardware write-blocker on PC-3000 UDMA, and it was confirmed to power and report at the disc level. A read-only image of the disk was created on DeepSpar to prevent any writing. The Mac filesystem (HFS+ or APFS) was parsed in R-Studio, which allowed us to rebuild the directory and volume structure from the image, and then the data was located and validated onto fresh media.
The filesystem was rebuilt from a read-only image copy of the drive, and your files were put onto brand new media. The diagnostic stage is free of charge and we report back within two working days of your media arriving, at which point we send you one fixed quote in writing, plus VAT, and in most cases you only pay if we recover your data. In other words, if a drive is visible but can't be mounted then the problem lies with its filesystem, so we make a read-only image of the drive and rebuild the filesystem from that without ever formatting it. Once it's rebuilt from the image, your files come back.
If the disk shows up as a disc but doesn't mount, that points to a problem with its filesystem, because the hardware side is working, so the drive is powered and reporting, but the filesystem (the part that organises the files on the disk) has become damaged and that is what stops the Finder mounting it. The fact that you can see the disk in settings but not in the Finder tells you where the fault is, since settings show every disc the hardware reports, while the Finder only shows volumes it can mount. The disk is imaged read-only, then the filesystem is rebuilt and the data recovered. If the Mac asks you to format the disk, don't let it, as formatting would put an empty structure over the top of your data, and the disk should be imaged and then rebuilt instead.
Every case file is anonymised and based on genuine enquiries that our lab has handled for customers from all around Swindon and Wiltshire. Each of the entries describes how our engineers approach a particular fault to diagnose it and recover the data, using the equipment listed.
A Reset Removes the Index, Not the Data — the Older Files Are Carved Back, an Honest Partial
A Reinstall Removes the Index, Not the Files — Untouched Since, They Carve Back Well
A Beeping Drive Is a Seized Motor, Not a Simple Jam — Freed Under Magnification in Clean Air
You will receive a free diagnosis along with a fixed quote before you send us anything, and in most cases you only pay if we recover your data. For electronic, mechanical and drive-opening work, 50% is due upfront and the balance only if we recover your data, while forensic work is paid upfront once you accept the fixed quote. Please always send us just the drive rather than the entire computer (if you're not sure what type of storage you have, ring us first). Take the disks out of any RAID or server and clearly label each one with its bay. When it's a NAS, try to take the disks out, but if they won't come out please send the whole NAS. A single external drive comes whole, including its cable and power supply. We recommend posting it tracked and insured, or you can drop it off at the Oxford lab, Monday to Friday, 9am to 5:30pm, no appointment needed. Start now or give us a call on the freephone.