Where did my backups go?
I’m using Time Machine to back up to a Time Capsule. Last week a message popped up saying “Time Machine completed a verification of your backups on Time Capsule. To improve reliability, Time Machine must create a new backup for you. New backup will remove existing backup history. This could take several hours”.
I’m somewhat reluctant for my existing history to be removed until I’m sure what has happened. I tried Disk Utility on the Time Capsule and it said the Time Machine backups were corrupt! What could possibly have caused this? June O’Keeffe
Your Time Capsule backs up onto a hard disk, and this disk is just as vulnerable to errors as the one in your Mac. The idea behind backing up is simply that it’s very unlikely both disks will fail at the same time. If your Mac disk fails first, you restore it from the backup. If the Time Capsule fails, then you recreate the backup from the files on your Mac. It’s true that you’ll lose the entire history of file changes in your Time Machine backup, but it’s better to have a single backup snapshot that works than many corrupted snapshots.
If the history of your files is important to you, then you shouldn’t rely on Time Machine to preserve it. At that point the data on your Time Capsule stops being a backup and becomes unique data that itself needs to be backed up!
Time Machine routinely verifies its own database structure to make sure you can trust your backup, and when it flags up a problem the best thing to do is recreate your backup immediately. If the thought of being temporarily without a backup makes you queasy, I suggest you do as I do and keep two backup sets. Let Time Machine back up, every hour, just the files that have changed, and also use a separate drive to periodically make a second copy of your Mac’s disk using software such as Super Duper (about £20, shirtpocket.com).