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CDR / Casebook / A Cyclic Redundancy Check on Everything Copied

Missing or corrupt files · case file · CDF-2025-0311

Every Long Copy Stopped at the Same Message.

A power cut caught the Toshiba in its dock on the office shelf, where it had sat for years. After that no copy would finish. Odd files at first, then whole folders, all halting at cyclic redundancy check. He swapped the lead, carried it out to the works laptop, and left Windows scanning it two nights running, and both mornings it was still going. The drive held thirty years of shop drawings from a fabricator in Trowbridge, east Cardiff: every staircase and handrail I have drawn since I started.

Outcome signed off by the customer No one is named here

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Why that happens.

The message is narrower than it sounds. It says the drive handed over a block, and the check value filed with that block disagreed. Nothing more. Two unrelated faults arrive at it: bookkeeping in a muddle on healthy hardware, or a platter that can no longer hold what was put there. The cure for one is the wrong move for the other, which is why guessing costs money. Windows meets a weak patch by pushing at it again and again, until either the sector answers or the drive gives up. He had given it two nights to push.

What we used on this one.

Every step, in order →
The toolsWhat it did hereWhy it helps
DeepSpar Disk Imager 4Imaged the Toshiba with retries capped, noting the awkward zones and pressing onMaps the heads first, works surface by surface, and keeps resets, timeouts and power in hand
R-Studio TechnicianPut the volume back together from the copy, not the diskReads nearly every file system, and rebuilds arrays you can rely on
ACE Lab PC-3000 ExpressOpened the firmware first: how the attributes were trending, the grown defect list, and those two all-night power-on sessionsOpens the maker's service commands, which a plain ATA link will not pass

How it went.

01

Ask the drive before you touch the platters

Not one sector was read until the firmware had spoken, and its answers were blunt. Reallocated sectors ran high and were still climbing, with a queue of others waiting to join them. Two vast power-on sessions in the log lined up with his two nights of checking, near enough hour for hour. That makes it a hardware fault, not muddled bookkeeping.

02

Retries cost time, so give them a limit

The rules were set before the pass began. Timeouts kept short, attempts capped, and anywhere that fought back logged, skipped and left alone. Those skipped bands got one quick second look right at the end. The arithmetic decides it. Fight one bad sector for an hour and you may lose the thousand good ones waiting behind it.

03

Switch the drive off, then work on the copy

With the image safely on disk, the Toshiba was powered down and stayed down. The copy read better than we expected. The folder tree was complete, and what had gone sat in one band, beneath a batch of scanned sheets. Each missing sheet was logged under its own name, so he went away with something to check against the plan chest rather than a vague apology.

Signing it off.

He had told us on the phone which folder came first: the stairs and balustrades for buildings that are still standing. It was opened and checked while the invoice was still unmentioned. The archive travelled home on a fresh disk, entire except for the sheets the report lists. Two he can draw again from paper kept in the office. The others belong to work finished before he took the business on, and that paper was thrown out long ago.

In brief: A CRC error is the drive telling the truth about itself. Take one clean copy while you still can, and stop asking it for more.

Is that what yours is doing?

Power it down, get it to us, and hold off on any decision until the diagnosis says what can still be read.

0800 6890668