Time Machine: not just for backups

Time Machine occupies just a few bullet points in Apple's list of 300+ new features in Leopard. But it has the ability to fundamentally change the way you and I use our computers.

Disclaimer: I have not actually used Time Machine. My only knowledge of it comes from the public videos and demos and from reading the Mac sites like MacInTouch and The Unofficial Apple Weblog.



From the Apple literature, Time Machine is an easy way to retrieve your lost files. It's being introduced it like that because it's simple to understand. If you've accidentally (or purposefully) deleted a file, you can simply use Time Machine to find it and bring it back. For this use, it's not much different from any other backup software. But the similarity ends there. This is not SuperDuper.

Time Machine maintains a complete history (at hourly intervals) of every file on your computer. To put it a different way, every hour it takes a "snapshot" of your computer and stores the way it looked at that moment. These snapshots comprise a set of "versions" of your files. Time Machine gives you a way to retrieve those versions.

Time Machine is not simply a backup of the way your computer's files currently look. The term "backup" implies a second copy of your current files. Stop thinking about backups. Start thinking about versions. Think about three, four, ten, hundreds of copies of your files, each representing the way it looked at a particular point in time.

Here are a few scenarios that use versions--rather than backups of lost files--as their centerpieces.

Have you ever worked on a long-term project? One that spanned more than a few hours? It could be a project for work. Or it could be that Great American Novel you've been writing. Or an iMovie project of your last vacation. You haven't deleted it; you've simply been changing it. Have you ever messed it up so badly (and saved your mess) that you wished you could go back to the way it was earlier in the day? With Time Machine you can. Just roll back through time to find the last good version of your project. You can use Quick Look to glance at the document to verify it's the one you want. When you find it, restore it.

Some documents are ever-evolving. For example, a real estate office may have a letter they mail out to new clients periodically. When they want to send out a letter, they just change the address and a few words here and there to customize it. Because the document evolves, today's version bears little resemblance to the one they sent out six months ago. What if they wanted to see what the letter looked liked back then and compare it to today's? They can with Time Machine. They don't even have to restore it; just use Quick Look to peek at it.

I'll leave you with this one final revolutionary usage of Time Machine. Most of us have an ever-increasing number of files on our computer. Organizing it all is becoming a chore. We download new files or create them constantly. They clutter up our folders and Desktop. It's maddening. And we should be backing it all up. Of course, you know that Time Machine will help you do the backups.

But think about this: Download or create a new file. Use it for its intended purpose now. Keep it around for an hour or two. Then throw it in the Trash. That's right: don't think about how you might want to use the file later. Never mind that your co-worker will be needing it next week. Or that you might want to refer to it next month. Throw it away now. De-clutter your life. Or at least your Mac.

Ah, don't worry. Time Machine has it. You can always get it back later. Spotlight can help you find it.

This may change the way we build computers. No longer will you need a gigantic primary hard drive that holds all your files, plus an equally monstrous hard drive to back up it all. Instead, your computer has a lean, fast primary storage device big enough to hold the files you're using right now. A few GBs of flash memory will do for most people. The rest--a complete history of every file you've ever worked on--is stored on a large-capacity Time Machine device.

That's the future of computing. Look out, because in a near-future release of OS X, I predict that Time Machine will be the filesystem. There will be no distinction between your "current files" and your "backup files." All your files, current or not, will simply be versions stored in a searchable database. Solaris' ZFS technology will help make that happen.

Backups, pt 1

We all need to do backups of our computers. Most of us don't. Let's take a brief look at the typical backup options available to us.

1. Manual backup to removable media, such as tape, CD, DVD, etc. This has been the traditional way of doing backups. The rationale (at least, until recently) is that removable media can store more data than hard drives. For example, about ten years ago, a high-end tape cartridge could store about 8GB of data wherease the largest hard drive you could reasonably obtain was about 4GB. Also, backups were supposed to be write-mostly, meaning that backups were to be read very infrequently. The linear nature of tape meant that reads were very slow, but that was a small price to pay for the relative low cost of the cartridges.

Nowadays, almost all removable media hold less than a hard drive, so this option isn't good for comprehensive backup solutions. Still, it's the preferred method among casual backer-uppers for keeping a copy of documents, photos, and so forth.

2. Automated backup to another hard drive. Given how ridiculously cheap hard drives are these days, this is my current method of doing backups. The backup drive is simply a large, cheap hard drive that keeps a copy of the data on my computer.

3. Automated backup to a network service. I like the concept of these backup services (Mozy, .Mac, Amazon S3). The storage is relatively cheap and you can be assured that the service itself is keeping backups, so you'll never lose your data. All your files are kept off-site, a big plus if your home or office is lost in a fire or flood.

For the automated solutions, there's a problem: the backups are performed at periodic intervals, such as every night or once a week. But the time you really need your backup is immediately after you realize you just deleted an important file. Ideally, the backup system should be making backups within minutes of making any filesystem change, whether it be adding, deleting, or modifying a file.

One easy fix that fits within the realm of automated, periodic backups is simply to reduce the backup interval. How about every five minutes? That would be swell. But that begets another problem: the actual time it takes to perform a backup may well exceed the backup interval! You see, typical backup applications figure out which files have changed by scanning all of your files and comparing the modifiation time to the last time the backup was made. My desktop computer has nearly a million files in it; scanning all of them takes a long, long time. It causes my computer to slow to a crawl, too, as system resources are consumed.

I hate doing backups. I dread seeing the pop-up window that appears, letting me know that backups are about to begin. My system will become unusable for about an hour. Ugh.

How can we speed it up and make it better? We need help from the operating system itself, something that most OSs don't natively provide to applications. Apple has a solution in its upcoming Leopard release. We'll talk about it in an upcoming post.