Data Recovery Case File · Trust, Practice & Honest Limits · Planning the Next Step

Sizing the Drive You Buy Next

This enquiry arrived after the device had already been handed in, and asked something nobody else in the archive has thought to ask. Having dropped off an external drive with a note, the owner added: "I also wanted to ask if you can, once the data is recovered, tell me how much storage space the Time Machine will require when I migrate it to a new Mac, as I want to ensure I order the correct size." Contactable by email while away. It is a small, sensible, forward-looking question — and it deserves a real answer, because almost everybody buys the wrong size, and the usual mistake runs in one direction.

The decode: the numbers that actually matter

Why the recovered total is not the number to buy against: the first thing worth separating. A recovery frequently yields more than the original appeared to hold — deleted files still physically present come back alongside live ones, earlier versions of documents surface, and where a filesystem rebuild is partial the output is delivered both as a reconstructed tree and as a carved set covering the same material. So the figure that comes off a bench is usually larger than the figure the owner remembers, and buying against memory is how people run out of space mid-transfer.

What a backup destination actually needs: considerably more than the data it protects, and this is where most people under-buy. A backup drive that is the same size as the material it holds can store exactly one copy and no history. The whole value of a versioned backup is that it keeps previous states — so that a file deleted or ruined last week can still be retrieved — and those versions consume space continuously. A destination sized at roughly two to three times the data being protected gives a useful depth of history; sized at parity, it fills quickly and begins discarding the oldest versions, which are often exactly the ones eventually wanted.

The related mistake on the new machine: a replacement computer should have room for the recovered material plus ordinary growth, not just enough to receive it. A machine that arrives 90% full is unpleasant to use and starts forcing decisions immediately.

What can be reported precisely rather than guessed: the useful part of answering this properly. Once a recovery is complete the actual recovered total is a measured number, not an estimate, and it can be given as a figure along with a breakdown — how much is live data, how much is recovered deleted material, and how much is duplication between the reconstructed tree and the carved set. That last distinction matters, because a customer who knows that a third of the total is duplicate output can plan against the real figure rather than the raw one.

The point worth making about what caused this: gently, because they are already planning ahead. A backup drive that fails is a single point of failure doing the job of a safety net. The replacement setup benefits from a second destination — another drive rotated occasionally, or an off-site service — so that the next failure is an inconvenience rather than an enquiry.

On the bench

Contact was kept to email throughout, as asked, since a customer who has stated how they can be reached should not have to chase a firm that has forgotten. The recovered total was measured and reported rather than estimated — broken down into live data, recovered deleted material, and duplication between the reconstructed tree and the carved output — so that replacement storage could be specified against the real figure. Destination media was sized above the source before writing began, since recoveries routinely yield more than the original appeared to hold.

The outcome

The recovery completed, the actual total measured and reported with a breakdown, and replacement sizing advised against real figures. 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, for anyone buying replacement storage: don't size against what you remember having, because a recovery usually returns more than the original appeared to hold once deleted files and earlier versions surface; a versioned backup destination needs roughly two to three times the data it protects, because its value is the history it keeps and a same-size drive fills up and starts discarding the oldest versions; and ask for the recovered total as a measured figure with duplication identified.

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.