This is the error you will see while chkdsk is running (sometimes there may be hundreds of “File record segment 12345 is unreadable” messages), and it indicates damage to the master file table, the index NTFS uses to locate your files. Usually it means bad sectors on a drive that is beginning to fail. Below is what it means, what not to do, and how the data is recovered.
The master file table is essentially a catalogue in which NTFS records every file on the volume. When chkdsk hits sectors in that table that it cannot read, it reports each one individually. If you receive a flood of these messages, it usually means your drive has physical bad sectors and is failing, which is why imaging should take place before any repair.
chkdsk /f or /r on a drive throwing these errors. Each chkdsk pass forces the failing disk to re-read and remap the same bad sectors, which causes additional stress, and there is also a risk that recoverable data could be overwritten. If the files matter, create an image of the disk first and recover the data from that image instead.NTFS keeps a master file table (the MFT), a catalogue split into small 1 KB “file record segments”, one for each file on the disk, recording where that file begins and ends. “File record segment N is unreadable” is simply stating that when chkdsk tried to read segment N of that table, the drive was unable to return it, but the actual file data is usually still intact on the platters. What cannot be read is the catalogue entry pointing to the file, and most often this is because the sector holding it has gone bad.
If you only have a handful of unreadable segments, they could all be coming from just one problem area, or a loss of power while writing to the drive. However, if chkdsk lists a large number of them (dozens or even hundreds), it almost always means the drive has developed widespread bad sectors and is physically failing. The key signs to look for: the scan crawls, the drive is slow, clicking or ticking, and the same errors return every time you run it. That is a hardware fault, and not something a software repair can put right.
You’ll often find that Windows keeps offering to run chkdsk, and it can be very tempting to let it finish. On a healthy drive with minor table damage, it can rebuild the MFT. On a failing drive, however, it does harm: every /f or /r pass forces the disk to hammer the same unreadable sectors, accelerating the failure, and chkdsk can also move or overwrite your files as it attempts to ‘fix’ things, turning a recoverable drive into a lost one. So unless you know the drive is sound, stop. Do not format it, and do not run repeated scans.
So what is the safe route? The drive is cloned onto a healthy one using a hardware imager that reads around bad sectors (retrying, slowing down and skipping what won’t come back), so the original is never written to and never worked harder than it can bear. From this cloned image, the master file table is rebuilt, or where it’s too damaged, the files are carved out by their signatures. A single hard drive or laptop or PC drive costs from £300 +VAT; an external drive is sent whole; a USB stick or memory card costs from £250 +VAT. Every job starts with a free diagnostic and a fixed written quote, and in most cases you only pay if we recover your data.
It’s a chkdsk error indicating that it was unable to read a portion of the master file table (MFT), the index NTFS uses to locate your files. The MFT is split into “file record segments”, one per file, and an unreadable segment usually sits in a bad sector. Your files are normally still on the disk; only the catalogue entry for them cannot be read, often because the drive is starting to fail.
Typically, no. The actual file data usually remains on the platters; the issue lies with the table indexing it. Provided the drive is imaged before it deteriorates further, the data can generally be recovered by rebuilding the MFT from the copy or by carving individual files out directly. The real risk is running repairs on a failing drive, which can overwrite recoverable data.
Only if you are certain the drive is healthy. A few unreadable segments on a sound disk can be repaired using chkdsk. However, a long list of them usually indicates physical bad sectors and a failing drive, and each subsequent chkdsk pass will stress the disk further and could write over recoverable data while attempting to rebuild the table. If the files matter and you are unsure of the drive’s health, image it first.
Because the drive has developed widespread bad sectors. Each unreadable segment represents a piece of the file table sitting in a sector the drive can no longer read, and a large number of them means the failure is spreading: typically the scan runs very slowly, and there may be clicking sounds from the drive. That is a hardware fault, so the fix is to image the drive read-only, not to keep scanning.
In most cases, yes. The drive is copied using a piece of hardware (an imager) that reads around the bad sectors so as to minimise stress on the drive. Once this copy is made, the file system is rebuilt from it. A single drive costs from £300 +VAT, always confirmed in a written quote following a free diagnostic, and in most cases you only pay if we recover your data. Please send us just the bare drive instead of your complete computer; a local shop will be able to remove it in a matter of minutes if needed.
A large number of unreadable file record segments usually indicates a failing drive. Do not run chkdsk again; send it to us instead, and we’ll make a read-only image of it past the bad sectors and rebuild your files from the copy. We offer a free diagnostic and a fixed quote before any work.