SuperDuper! Pro Tip

As much as I love my new MacBook Air, the transition to the new machine hasn't been completely seamless. Like any transition to a new computer, there are bound to be hiccups. One of these hiccups was around my backups. Since I take my backups very seriously, this was something that really bothered me until I was able to figure out what was going wrong.

After migrating all of my data to the new machine I made sure to run SuperDuper! (the best disk cloning software in the universe). It ran perfectly for quite some time but after a few weeks it started to fail by running out of disk space on the backup drive.

When I first partitioned my backup drive I made the clone parition the same size as the boot drive: 120GB. But the MacBook Air has a larger drive in it, double the size at 250GB. I've been careful to make sure that I don't use more than 120GB on the new machine, so surely the problem wasn't that I was using more space than I should be. Or at least that's what I thought.

It turns out that Lion comes with some enhancements to Time Machine. Under Lion, if your backup drive is not connected, Time Machine will continue to run. The backups are stored in /.MobileBackups -- a hidden folder at the root of the boot drive. Since this is effectively temporary storage, Lion doesn't report any of the space used by this directory in the Unix disk free or df command or in the Finder. Essentially, Lion hides the fact that it's using this space from you at all. It does this because it will automatically remove old backups to make room for new files written to disk if need be.

Since SuperDuper! didn't know this it would attempt to copy this directory to the backup drive. Ordinarily this wouldn't be a problem since the clone drive is usually the same size as the drive being cloned. This wasn't the case for me however. After I figured this out I created a new backup script and excluded the /.MobileBackups directory. After applying the changes I haven't had any problems.

So, if SuperDuper! is complaining about running out of disk space when running on Lion, you might want to either:

1. ensure that the size of the drive you're cloning from is the same size as the drive you're cloning to. or;
2. exclude /.MobileBackups from your SuperDuper! backup script.

MacBook Air

A few months back I bought a new MacBook Air. I absolutely love it, it's the best computer I've ever owned. I'm pretty sure I say that about every new computer I get, but this one is head and shoulders above the rest.

Upgrades in the past used to be just incremental updates to the processor, memory, and hard drive. This machine has all of that, but what's amazing is how much faster it feels than every other upgrade I've done. It's really no surprise when you think about it.

There are really only 2 main driving forces that relate to the performance of any application: its use of the procesor, and its use of the hard drive¹. Yes, I'm simplifying here, but typically when you want to optimze a program you need to look at those 2 things.

When a program uses a lot of processor cycles its said to be CPU-bound. That is, the program's performance is bound by the speed of the processor. Conversely, when a program reads and writes to the hard drive a lot it's said to be I/O bound; the performance of the program is bound by how quickly it can read and write data. Very rarely will you ever see a program that's solely CPU bound or I/O bound. Usually different parts of every program have different performance characteristics.

So why is it no surprise that the MacBook Air feels so much faster than any other computer I've ever owned? The MacBook Air has a solid state drive. Solid state drives are a new class of storage media. They optimize for speed while sacrificing total size. To give you an example, you can buy a 256GB SSD for roughly the same price as a 4TB spinning rust² drive. But the speed of these drives is amazing due to how they work. SSDs have more-or-less direct access to any piece of information on the drive. Traditional hard drives have to wait for a spinning platter to come within range of a little arm that can picks the data off the drive. There are physics involved here, traditional hard drives will never be as fast as an SSD, but if you need a lot of storage space you can't go wrong.

You can get an SSD for pretty much any computer, but at this point they're a fairly expensive upgrade. It's been said before that installing an SSD is just like getting a new computer. And while my MacBook Air is certainly a new computer, it feels amazing every time I use it. It's fast. Faster than anything I've ever used before, and that's mostly thanks to the SSD.

There's a lot more that can be said about the MacBook Air. It's simple, tossing out things that most people rarely need anymore like DVD drives, FireWire, and extra USB ports. It's ultra lightweight, something that's really nice to have regardless of whether you care about the weight or not. The choices you have to make are pretty minimal; pick a screen size, processor and memory. The price is very reasonable for a premium product. The fit and finish is excellent. All told, the MacBook Air truly is the Volkscomputer.

1. Yes, I'm simplifying quite a bit here. Performance can also be affected by how much parallel computation a program can do, the layout of the program in memory so that it makes efficient use of the CPU's caches, etc.
2. The term spinning rust refers to the fact that traditional mechanical hard drives contain rust colored platters that spin. Wikipedia has a great article about how these types of drives work.

5 Things You Can Do to Ensure Safety of Your Data and Recoverability of Your Computer

In my previous article I described some of the problems with the approach most people use to secure their data. The problems were all essentially the same: security theatre. In this article I'll outline 5 things that you can do to ensure that your data is safe and increase the likelyhood that you'll be able to get your computer returned.

The advice in this column isn't meant to be prescriptive. Instead, read through the suggestions and make sure that they make sense to you, and for your situation. If you have backups and don't need to be bothered with ensuring the returnabilty of your computer by all means, tighten your machine down. If you're like the rest of us, read on.

1. Backup Your Data -- Offsite

This one's a no-brainer. Backing up your data is one thing, but making sure that you have a good copy of it off site is another. If someone breaks into your house a backup isn't going to be much good to you if it's sitting on the external hard drive conveniently located next to your computer. It doesn't matter if you use one of those automated off site backup solutions like Backblaze or Carbonite, or if you use an old fashioned sneakernet like me. Just make sure you have a recent copy of your data off site.

2. Make Your Computer as Inviting as Possible

If you're used to a higher level of security, this tip might not make a ton of sense. It's true, your computer will be wide open if you do this. While you may want to lock down your computer for the most part, in order to ensure the safe return of your computer you'll want me make it as easy and inviting as possible for a thief to use your computer. If you make it too difficult either they'll never use it, or they'll find someone to wipe it clean so that they can start fresh. If they do the latter you'll never see your data again.

So what do I mean by "make your computer as inviting as possible"? I mean that you should:

1. Set up your account to automatically log in.
2. Remove a power-on password
3. Remove disk encryption

By doing these things you'll ensure that anyone that sits down at your computer will be able to use it for whatever purposes they want. It also means that everything on your computer will be wide open to anyone that wants access to it. To fix that you're going to want to:

1. Lock your keychain
2. Use encrypted disk images

3. Lock your Keychain

The Keychain Access application on the Mac is the unsung hero of password management. Applications use it to store credentials for web sites you go to and services you use. The Finder uses it to store passwords for remote file shares, logins for wireless access points, etc. By default the password to unlock your keychain is synchronized with your login password, and the Keychain remains unlocked while you're logged in. These defaults optimize for user experience, not necessarily security. But hey, at least these can be configured.

To change these settings your going to want to open the Keychain Access application and open its preferences. From the preferences window select the First Aid tab and uncheck the last 2 checkboxes: Set login keychain as default, and Keep login keychain unlocked.

By changing these settings you will need to enter your password whenever an application wants to access some data within the keychain. This will certainly be more annoying than the default settings, but your passwords and anything else stored in the keychain will remain safe should your computer fall into the wrong hands.

4. Use Encrypted Disk Images

As I discussed in a previous post, encrypting your entire hard disk is a one way street. Your data will be safe if your computer gets lost or stolen, but it also means that the computer is completely useless to anyone that finds it. But what if you have sensitive data on your computer? Clearly you want that data to be secure, you just don't want blanket security across the entire hard drive. That's where encrypted disk images come in.

Disk Utility will allow you to create encrypted disk images to store any sensitive data. You can make them virtually any size you want, and use either 128- or 256-bit AES encryption. As of later releases of Mac OS X you can also use a sparse image format. Sparse formats allow you to create a disk of virtually any size, but it will only take up as much physical space on disk as the files that are contained within it. For example if you had a 500MB sparse image but only put 50MB of data in it, the image on disk would only be about 50MB. The best format to use a whole other discussion. But for our purposes, it doesn't matter which one you pick, just make sure its encrypted.

Once you have an encrypted disk image you can then store all of your files within the image. Images can be configured to be mounted automatically upon login by adding them as a login item, but if you don't need to access those files very frequently, its best to leave the images un-mounted until they're needed.

With all of your sensitive data stored in encrypted disk images you can be assured that your data will be safe if your computer gets lost or stolen.

5. Install a Snooping Tool

Lastly, to have any hope of getting a stolen computer back, you're best bet is to install a snooping tool. These tools take screen shots and pictures with a computer's camera, report location and IP information, and do many other things to snoop on a thief or help get your computer back. An excellent and free tool that does this is Prey.

Once installed, Prey sits idle until you log into the web site to report your computer as lost or stolen. From there you can configure it to snoop on the thief at selected intervals. By using information gathered by Prey and the help of police many people have been able to retrieve their stolen computer.