The Time Machine Quandry

There’s been a lot of noise about the Time Machine feature in Leopard. The idea isn’t new, functionally it appears similar to Shadow Copy in Windows Vista. It has a flashy interface which looks good in demos, but I’d almost prefer Microsoft’s right-click and select from a menu. Maybe I’m just turned off by flashy demos because I figure they’re hiding something. Maybe making backups fun is a good thing that will get people to do them. But, all that aside, I have a good backup process and I don’t see Time Machine as a change for the better. But hey, it’s new and I want to try it, so what’s the best way for me to use it?

I haven’t used Leopard yet but here’s what Apple tells us about Time Machine:

  • Backs up everything by default, but it can be changed.
  • Any directly connected external drive gets offered as a time machine drive the first time it’s connected. although Time Machine can backup to another drive over the network.
  • Multiple Macs can use the same Time Machine drive.
  • Time Machine can restore the entire computer if needed.
  • The initial backup is the entire hard disk, without compression. After the initial backup only incrementals are done.
  • Time Machine can be used to migrate settings to a new Mac.

I have a 30-day file history through Mozy. While Time Machine will keep things “forever – up to the limits of disk space” I’ve never had a problem with the 30 day limit and Time Machine could actually be less than 30-days depending on disk space. Mozy gives me an offsite backup so I’m not going to dump it for Time Machine.

The other thing that has me concerned about Time Machine is the disk space usage. Keeping all files forever takes a lot of disk space so Time Machine will have to purge old backups. Apple says they’ll be a notification before this happens. I’m hoping this is a one time notification and not a constant nag each time some deletion is needed. The problem with this is the historical archive duration is based upon the size of the Time Machine disk so the actual history may vary over time and isn’t a set duration. The size of the Time Machine disk is based upon the size of you Mac disk (or at least the files on it) so your Time Machine disk needs to be larger than your data with enough extra space to save changes for how ever long you want. Figuring that out seems guesswork at best. What happens if you edit large movie files all the time? I have visions of Time Machine filling up rapidly.

What would be intriguing (but costly) is to team up Time Machine with Drobo. As you run short of disk space you can simply expand Drobo without losing any past data. There’s no mention by Apple as to whether you can manually delete old files as of a certain date. Since Drobo reports itself as an insanely large disk (2TB) so Time Machine would never see the disk run out (well, not until it actually used 2TB). You monitor available space through Drobo and to avoid having to keep buying disk upgrades you have to manually delete from Time Machine. Since I don’t have a Drobo I can only dream.

Since my disk clone is local I could use Time Machine to replace my nightly disk image backup. One benefit of the disk image backup is I can immediately boot from backup by holding down the option key. While Time Machine can do a full restore, the Time Machine disk isn’t bootable since the backup is in directories and not as an image. Since disks always fail at the worst time this could add several hours to the recovery process when I really need to use the computer. I don’t see Time Machine replacing my SuperDuper! disk clone.

I do have two Macs that don’t get backed up in full. My MacBook only gets it’s settings and data backed up to Mozy. My Mac Mini doesn’t get backed up all. It would be nice to have a full backup of these machines. So I plan to hook an external drive up to my Airport Extreme and try to use Time Machine by connecting to this drive with both machines. [Updated: Oct. 26 – There’s been confirmation that Airport connected drives can’t be used by Time machine.] The Mac Mini will be interesting because large video files come and go on it with great frequency. It’s also got a slower 802.11g wireless connection.