A Dropped External Hard Drive Should Stay Unplugged, Engadget Report Says
Engadget reports that a dropped external hard drive should not be plugged in for a quick test, because spinning a damaged drive can scratch its platters and cause permanent data loss. For important, unbacked-up data, the report says professional evaluation is the safest route.
Although an external hard drive may look sturdy, its enclosure contains moving parts, sometimes including glass, and its read/write heads and platters normally operate only nanometers apart. A fall can close that gap. The data may still be intact after the impact, but starting the drive forces the heads back over the platters and can scratch the magnetic surface, Engadget says.
External hard drives spin at 5,400 or 7,200 RPM, and that speed helps damage spread. If the heads were misaligned by the fall, plugging in the drive can scratch the platters. Debris from the first scratch can then be caught in the spin and contaminate other parts of the platter surface. The risk is higher if the drive was running when it fell. Each additional spin-up can make recovery harder because technicians normally replace damaged parts with donor parts and copy data from the platters bit by bit.
Engadget says a drive that takes a serious hit should be treated as damaged until proven otherwise, especially if it was running at the time. The drive should not be plugged into a computer, and it should be unplugged immediately if it is still connected. Tapping, shaking, opening or freezing the drive can worsen its condition if it was damaged.
If the data on the drive matters and is not backed up, the report says it should go to an established data recovery service before any risks are taken. If the data is less important or the owner is willing to take the risk, Engadget describes a careful single test: plug in the drive and listen closely as it spins up. If it makes abnormal noises such as clicking, beeping or grinding, or if it repeatedly restarts, it should be unplugged immediately.
If the drive mounts and operates normally, the next step is to copy the most important files off it before running diagnostic tools. After that, the drive's SMART data can be checked with tools such as CrystalDiskInfo. Warnings such as reallocated or pending sectors mean the drive should be treated as unreliable and the rest of the data moved to another safe location. Engadget notes that some USB enclosures cannot report SMART data, and that passing tests is a good sign but not a guarantee of ongoing health.
The report also says habits such as not moving a drive while it is running, ejecting external drives properly and storing retired drives safely can reduce the risk of damage.