Tag Archives: files

Two copies is not enough

Image © Norlando Pobre; licensed under Creative Commons

A friend of mine, who shall remain anonymous, today lost nearly 1TB of data after a disk drive failed. The disk was mirrored, so it may still be recoverable, and indeed they have recovered about 750GB from the damaged disk, but they don’t need me to tell them that a robust backup setup would have saved them the cost of that recovery software, and the stress of potential loss of data.

A disk can fail at any time, for no reason, and with no warning. This fact should be at the back of your mind every time you consider your data storage setup. If it worries you, it should, but a good backup regime will help to minimise that worry.

At no point in time should you ever have only one copy of a file. This is the foundation of a good backup schedule. When you are taking photos, if you have a camera that supports multiple cards, ensure you have the photos written to both cards simultaneously. The next best thing is to ensure you import the images to your computer as soon as possible and as regularly as possible. If you have enough cards, don’t delete the images from the cards until they are fully incorporated into your backup system. If your hard drive fails, and you’ve formatted your card, the images are lost.

So, let’s say you use have a regular backup of your files, such as Apple’s Time Machine or an equivalent. Are you safe? If your computer’s hard drive fails, then you are left with just one copy of your files (on your backup disk) which is exposed and vulnerable to drive failure until you are able to replace and restore the drive. If anything happened to your backup disk during this time,  your data is lost again. Ideally, your important data should be stored initially on a RAID mirrored drive, where two disks contain identical data so that even if one fails, the other is still functional, and you still have a second copy on your hourly backup.

OK, so what happens if your house burns down? All three copies of your data could still vanish without trace. But there is still more that you can do. Services such as Backblaze act as a third line of defence against data loss. For a fixed monthly or annual fee, Backblaze will back up all your data (except for items that can be more easily recovered, e.g. applications for which you still have the installer disks or which you can re-download from the publisher) every hour. There is no limit to the amount of data you can store (I currently have 1.6 TB of data backed up to Backblaze) and being offsite means that you can recover all of your data even if your house or office is physically damaged. It may take several months for your first initial backup, depending on your internet connection speed, but once that first backup is complete your data is even safer.

If reading this doesn’t make you want to review your backup regime immediately, you’re either already sorted, or beyond help! Just ask yourself what you would do if all the data on your disk vanished in the next minute.