I recently upgraded my Mac to Leopard, whose marquee feature is Time Machine, a nice backup mechanism.

I already had a NAS box. I originally got this primarily as a backup target. It’s got a half-terabyte hard drive in it, and it supports AFP, so it seems like a logical target for Time Machine backups. And apparently in the betas of Leopard, it was possible to use a hard drive attached to an Airport Extreme as a Time Machine target. This was disabled in the shipping version, but there’s a simple hack to re-enable it. Which I applied: as it happens, this made also it possible to use Time Machine with my NAS box.

One critical difference between my NAS box and a hard drive hanging off an Airport Express is the disk format. Time Machine requires an HFS+ disk. My box is using something else. Time Machine actually deals with this cleverly by creating a disk-image file on the target drive, but that’s also the root of the problem: Mounting this disk image over the network (even GigE) gets slower and slower as the file gets bigger and bigger. I had set up a very stripped-down backup profile (home directory only, no media files), but still, after a couple of weeks, it had gotten to 42 GB and took forever to mount. Eventually it took so long to mount that Time Machine would stop waiting for it and give up.

So until I get a Time Capsule or something, I’m using my previous backup app, Synk. Even after, it might be worth it to use Synk to back up my media files, which don’t need quite the obsessive hourly backup that Time Machine offers.