Data Recovery Case File · Desktop Externals & Aging Drives · Two Formats, One Drive
Which Volume You Can See Depends on the Host, and Which You Can Read Does Not
His enquiry separates two things that are easy to confuse. A 4TB drive with two volumes in different formats, no longer shown by the system, where "the disk is spinning, and sometimes it shows the first volume, but I cannot copy files from there." Appearing and being readable are different achievements — and with two formats on one drive, the first depends on what the computer understands while the second depends on the drive.
| Media | 4TB external hard drive carrying two volumes in different filesystem formats — rotation present, one volume intermittently presenting, content not copyable |
| Reported situation | External drive no longer shown by the host · drive audibly rotating · drive divided into two volumes in different filesystem formats · the cross-platform volume occasionally appearing · files not copyable from it when it does · second volume never appearing · content required |
| Fault class | Intermittent presentation with read failures on access — volume visibility governed by host format support, readability by drive condition |
| Equipment used | Volume visibility separated from volume readability · both volumes located from partition structures irrespective of host format support · imaged write-blocked under strict per-sector timeouts during periods of presentation · marginal regions revisited across later passes · both filesystems interpreted from the image |
The decode: two separate questions, and why only one concerns the drive
Why the two volumes behave differently on his machine: one is in a format the system reads natively and the other is in a format it also supports, but they are handled by different components. A host presents the volumes it can interpret and stays silent about those it cannot — which is a statement about the computer.
Why that must not be read as a fault: a volume not appearing may be perfectly intact. Absence from a host's list can mean unsupported, unmounted, or unreadable, and only the last concerns the drive.
What is done about that: both volumes are located from the drive's own partition structures rather than from what the host offers. The partition record describes every volume regardless of whether any machine can mount it, so nothing depends on format support.
Why the second observation is the substantive one: when the first volume does appear, files will not copy. That is the drive failing to return data, which is a fault rather than a limitation — and it is the same in any host.
What "sometimes it shows" indicates: presentation is intermittent. The drive completes its introduction on some attempts and not others, which is characteristic of a device that is marginal rather than failed.
Why the rotation being audible narrows things: the motor runs and the platters turn. Power, spin-up and mechanical function are established, so the difficulty lies in reading rather than in operating.
What the combination points at: read failures serious enough to prevent copying but not to prevent the volume being identified. Structures at the volume's start read well enough for it to be recognised, while the regions holding files do not.
Why the intermittency is the urgent part: the periods of presentation are the opportunity. They typically become less frequent, and each connection spent testing is one not spent capturing.
Why an ordinary copy cannot exploit them: it proceeds in folder order and stalls at the first unreadable file, then loses the drive when it withdraws. Nothing is secured before the window closes.
What is done instead: imaging under strict per-sector timeouts during periods of presentation, healthy regions first, marginal ones revisited across later passes — and both filesystems interpreted afterwards from the image, where format support is a matter of software rather than of the drive.
On the bench
Volume visibility was separated from volume readability — a host presenting volumes in formats it interprets and remaining silent about others, so absence from a host's list may mean unsupported rather than damaged, whereas failure to copy from a volume that does appear indicates the drive not returning data. Both volumes were located from partition structures irrespective of host format support, and imaging ran write-blocked under strict per-sector timeouts during periods of presentation.
The outcome
Volume visibility separated from readability, both volumes located from partition structures, and imaging performed during periods of presentation. Free assessment, one fixed written figure including VAT; where a drive has to be opened, 50% of parts and labour is payable upfront with the balance only on success — otherwise no recovery, no fee. The decode: which volume you can see is about your computer, and whether you can copy from it is about the drive. Only the second is a fault — and both volumes are found from the drive's own records regardless.
A drive with two volumes where only one ever appears
Stop reconnecting to test which shows up today — the periods when it presents are the opportunity, and they become less frequent. Separate the two things you're seeing: which volume appears depends on what your computer can interpret, so absence from the list may mean unsupported rather than damaged. Files refusing to copy from a volume that does appear is the real fault, since that's the drive failing to return data. Both volumes are found from the drive's own partition records regardless of what any machine will mount, so format support isn't the obstacle it appears to be.
Stop testing it — call Manchester Data Recovery on 0161 871 0788; visibility separated from readability, both volumes located from partition structures, imaged under capped timeouts during presentation.
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Our case files are drawn from genuine enquiries received by our laboratory over the past ten years, anonymised to protect client confidentiality. Each one describes the diagnostic and recovery procedure our engineers apply to that fault, using the equipment listed.