Wednesday, July 30, 2008

The dinosaur in the mirror

With two businesses and a photogenic family, I like to keep a lot of data handy – customer records for quick research, several Snowball translation memory databases, and all those family pictures for the slide show gadget. In the past, I've always been able to keep up with bloat by buying a new laptop with a bigger hard drive and backing up on a single external drive. But when my latest hard drive finally started overflowing and Duplicate Checker ran out of ways to create more space, it was finally time to get a bigger USB hard drive and offload some data. Where before I had all my data on local drive D: with nightly backups using SyncToy's Echo to USB drive F:, I now also had the original of my /General folder on drive F:, still with plenty of room for the backups. On the new and even bigger USB drive G:, there was room for SynchToy's Contribute to back up my /General files as well as the entire contents of C: (OS) and D: (data). Things were a bit sloppy on F:, with F:/Mirror of D and F:/General, so to clean things up a bit, I put all the backups on G: under the /Precision folder. Wonderful, now I was doubly protected, and there was still room in the backpack to take F: along with me on "vacation".

SyncToy folders:

When I got back from vacation, plugged everything in, and saw the orange daisies in the Slide Show gadget, I was slightly annoyed. When the Slide Show settings said "F:/General/Scrapbook", annoyance became concern. When I found F:/General/Scrapbook empty, concern became alarm – somehow, all of my pictures had disappeared, along with a lot of other important stuff! But my alarm was brightened by relief – after all, I must have gotten that new hard drive just in time. So I pulled up G:/Precision/General and… hairs-on-end panic.

More fatal than the blue screen of death – the orange daisies of destruction:

What had happened is that, when I plugged everything back in on my desk, drive F: became G: and drive G: became F:, and Task Scheduler, celebrating the return of the prodigal drive G: gleefully got to work. Since it found no /General on drive F:, it created one and copied its contents to G:/Precision/General. The effect was the same as having all builders and miners and no floaters – as far as I could tell, my precious files were pushing up the orange daisies.

This story has a happy ending. Because of my inconsistent naming of folders across disks, neither the original files nor their backups were erased, and by relettering the two USB drives I was able to get back to work fairly quickly, although it took a while for my hands to stop shaking. Using "Contribute" instead of "Echo" is also a safer way of backing up, if you've got the room. But it's all too easy to envision a case where, at the very least, everything since the last backup would be irretrievably erased.

When you plug in a USB device, Windows assigns it the first free drive letter it can find, and apparently does not remember these assignments. That's one dinosaur that nearly ate my mirror! I suppose that assigning drive letters to devices as I have now done will "reserve" those letters and prevent their being overwritten, both virtually and physically, but I'm not planning to take the risk of assuming that to be the case!