Technology

I first heard about recovering data from bad hard drives by placing them in a freezer from a web comics. The artist almost lost a lot of his work to a failed hard drive he hadn’t backed up. I’ve had my share of hard drive problems and have kept regular full backups for the past few years, so I’ve never really had an opportunity to try out this technique. But recently a good friend of mine had a hard drive go bad in her five year old MacBook. This seemed like the perfect opportunity, and I was pretty amazed at the results.

Classic Macbook with the hard drive removed

Years ago I had a black MacBook just like this one. It was one of the last models that was very user serviceable. The battery detached externally and thee screws revealed both the memory card slots and the hard drive. This type of design was most likely the result of the 2004/2005 iPod lawsuits in which Apple told customers to simply buy new iPods instead of either servicing or providing replacement batteries. Since then, Apple has gone back to fully enclosed cases, although they are still (unofficially) user serviceable for those with the skills and the right screw drivers.

Mac Hard Drive in SATA to USB Case

I hooked up my friend’s hard drive using an external SATA to USB adapter and heard the classic click of death. It was fairly loud as well, so I wasn’t very confident the freezer trick would work. I started reading a lot of conflicting reports, some stating this was entirely and urban legend or that it only worked with older hard drives. Considering this drive was five years old and had a clear hardware failure, there was no harm in trying.

Hard drive placed in two ziplocked bags

Looking through the various blog posts, I decided the best course was to wrap the drive in two separate zip lock bags and place the hard drive in a freezer overnight. Using two ziplocked bags is essential to preventing damage from condensation.

Hard drive in freezer overnight

Get out as much air as possible and wrap the bags tightly. Remember this is entirely to prevent condensation and water damage. I’m not sure what the coldest part of the freezer is, but I just left this hard drive in the centre of the middle rack.

Reading data from the hard drive while it’s still in the freezer

Some instructions tell people to remove the hard drive from the freezer, place it back into a desktop or laptop and retrieve the data as quickly as possible. Typically you have less than an hour before the hard drive will warm back up and potentially start clicking again. Other instructions recommend leaving the disk in the freezer while reading it. This was only a 160GB and I realized I could read it rather quickly, so I decided to leave it in the freezer. It took around twenty to thirty minutes to copy the contents of the person’s home directory and to look at the rest of the drive and make sure they didn’t have any data stored in other locations on the disk.

Copying data from the hard drive while it’s in the freezer

When I plugged in the hard drive, I got a warning that there were errors and the hard drive could only be mounted read-only to copy data off. I didn’t hear any clicks or get any serious IO errors during the copying process. The data seems to be entirely intact. After I copied everything off, I removed the hard drive from the freezer to prevent any condensation damage.

So in conclusion, in this situation the freezer trick worked. I had a totally dead hard drive. It was clearly clicking and would not be recognized at all when I plugged it in. A night in the freezer got the hard drive functioning enough that I could retrieve all the user data. This of course is no replacement for actual backups. My friend was extremely lucky and I’ll be sure to get her set up on a real backup solution going forward.

So the big question I had: why does this work? One theory I’ve read says the platters get warped over time due to heat and wear. The clicking is the sound of the heads scraping against the platters. Normally the heads don’t touch the hard drive platters. They’re magnetic and read data by hovering above the disks. By freezing the disk, the platters shrink enough the heads can clear the disk and retrieve data.

Other theories state the clicking comes from the motor not able to turn due to seized ball bearings. Freezing the hard drive can help free the spindle so it can turn again. Still others say that the head control springs and powerful magnets in the hard drive can wear out over time and freezing them can help strengthen the springs and magnets temporary.

There are also many links stating that freezing a hard drive doesn’t work or might be dangerous. Not surprisingly most of these links go to manufacture websites or to blog posts from data recovery companies that charge high fees for recovering your data.

This trick obviously won’t work all the time. If you don’t hear a physical click from your hard drive; if it’s not a physically bad hard drive but rather a faulty controller board, then this trick probably won’t work.

Data recovery companies have very sophisticated tools that can read data off hard drives that have been burnt, frozen and even crushed. In fact, you can never really wipe a traditional platter based hard drive. Even writing them over with tons of random data, due to the way that data is stored magnetically on a disk at the atomic level, a recovery company can go back several hundred, if not thousands, of writes. Although for a regular technician at home, this is impractical, forensics companies with clean labs have done this for years in law enforcement. Governments with secrete information typically require that hard drives be either shredded or melted after they are decommissioned; never re-purposed.

So if you do hear a click on a dead hard drive, using the freezer trick won’t hurt your hard drive (so long as you remember the double bags) and could save you a bit of money, should you be willing to pay for professional data recovery. Of course the best way to recover your data is to not lose it, using backup hard drives and on-line storage solutions.