I had a glitch…

I guess once you start talking about backups it never ends…

See, after getting everything set up and to my liking, I found much to my annoyance that I had a glitch.

Under random circumstances, my backups would fail, usually with some kind of “can’t create directory” error.

Glitches suck, because they can be tough to debug — because by definition glitches work properly most of the time. And usually fail when it’s inconvenient to debug. Fortunately, I’d seen this one before, but I thought I’d write about it for others who might run into it.

The first thing to try in these cases is simple: Disk Utility. It’s very possible that somewhere along the way the disk got corrupted and that’s causing your problem. Tried that, but the glitch came back, so that wasn’t it.

Buried in the Energy Saver System Preference is one that says “Put the hard disk(s) to sleep when possible”. Apple seems to default this to on. I have always turned it off; in the early days of Mac OS X there were disk drivers that had problems with it and would cause glitches. Over the years things got better, but I still have never really seen any real advantage to it.

So I turned it off.

And the glitch went away. Case closed.

But here’s what seems to be happening. When Time Machine fires up (I think I saw it once with Superduper, but in general, Superduper isn’t sensitive to this, Time Machine was VERY sensitive to it) sends out a disk write request to create the backup directory. Not sure who’s to blame for the glitch, but if the disk is spun down, Time Machine doesn’t wait and reports it as a failure. Not sure if this is the driver returning a “not ready yet, try again later” that Time Machine is seeing as an error, or if Time Machine has a timeout and if it doesn’t get the response back fast enough it errors, but either way, if you ask me, the software should really be smart enough to recognize this situation and do something useful, and “error out and abort” isn’t my definition of useful.

My recommendation: turn it off. Or at the very least, turn it off when attached to the power adaptor. And quietly ask yourself why Time Machine isn’t smart enough to deal with this situation, when, well, it’s kinda it’s JOB.

To take it a step further, what if this hadn’t fixed the gltich? what next?

For me, the next step would have been to put the drive mechanism into a different housing — it’s living in that removable dock, which is new to me, and I’d need to figure out if that housing was the cause or the drive itself (which is also new). If the glitch follows the drive, it’s probably got a problem and you ought to see about having it replaced under warranty. If it goes away in the new housing, then it’s the old housing, and you have to figure out what to do, whether it’s replace or reduce your dependence on it or whatever. There are, fortunately, only so many parts to these things, so this kind of replacement swap isn’t hard to do and can quickly help you find which piece is the core or the problem.

On a related note, Laurie’s main data disk (2x500Gb mirrored raid) filled up, so we had to find more room for her. The fast reaction was to shift her to a 750Gb drive I had handy, but we ordered 2x2Tb drives and I’ll be fitting them into the RAID this weekend and that’ll give her some room to expand. It also creates complications on her backups I’m still trying to figure out how best to solve, because her backup disks are big enough for her data set, but now for the size of the data set she’s going to grow on those new disks. We have time, but I want it solved before it’s a problem.

This has me rethinking Drobos. Drobo just announced a NAS, which looks interesting, but you can buy two “plug into the computer” Drobos for the cost of the Drobo NAS, and that’s an intriguing option as well. I’m guessing the long-term answer is a Drobo on each of our primary machines and a Drobo NAS for backups, but how to build them out and in what order, I’m not sure yet.  and honestly, there are other things I’d rather spend my money on, than backups.

But I’d rather spend money on backups than Drivesavers, ya know?

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