Does Constant Time Machine Activity Compromise Disk Longevity?

MacUser's Derik DeLong has highlighted a troubling issue related to Mac OS X 10.5 Leopard's Time Machine backup feature, which I just love, as it takes most of the tedium and hassle out of routine hard drive backups.

DeLong says that over many years of using the weekly hard disk clone backup mode, he never suffered a catastrophic disk failure, but with Time Machine's arrival he gave up his cloning ways and switched to an external two disk RAID setup for backups. Unfortunately his backup RAID has suffered a catastrophic disk failure.

DeLong says he wonders if the regular (sometimes near constant) disk access of an always-connected Time Machine backup setup puts undue stress on the hardware for that purpose?.

How can it not?

I was skeptical about Time Machine when it was first announced as a Leopard marquee feature enhancement, but I quickly became a convert. Time Machine is slick. Basically, you just connect an external hard drive and let it do its stuff with no fuss or bother. It's the slickest backup software I've ever used by a wide margin.

Annoyingly Noisy

However, I would find having Time Machine running constantly in the background rewriting every trivial little change in my hard drive data would drive me bananas. Of course, I use relatively slow Macs, but I find any sort of constant disk activity going on in the background annoying and distracting. And it stands to reason that all that relentless disk activity is not only going to exacerbate wear and tear on your backup media, but also your primary hard drive in the computer.

No thanks.

My backup regime is a bit unorthodox and idiosyncratic - and certainly not belt-and-suspenders certain to ensure that every jot and tittle of work is backed up at any given time - but so far it has worked for me. My primary backup is now via Time Machine, for which I connect an external Maxtor 500 GB external USB 2.0 drive in a SimpleDrive Pininfarina housing. I do updates periodically, but most of the time I keep Time Machine turned off. I just couldn't stand having that 7200 RPM 3.5" drive, which is a literal screamer, spooling up and powering down all the time and the disk chatter of Time Machine's hourly busy-busy going on.

My second line of defense is to every couple of weeks or so do a manual backup by dragging everything that's been changed to a second Mac via ethernet or FireWire Target Disk Mode.

I know I'm risking some data loss by not running constant backups, but so far so good, and if there's something in particular I really couldn't risk losing, I can always plug in the backup drive and run a Time Machine session.

This is not a prescription or a recommendation, just a report, and if you have zero tolerance for data loss, best to put up with the racket and system slowdown and keep Time Machine running.

However, for my purposes I also need the USB port for a variety of other things, and, yes, I do have a 4-port USB hub plugged into the PowerBook's other USB port - and it's oversubscribed as well.

Hard Drive Failure

While my periodic and targeted use of the Time Machine feature is not likely to substantially hasten catastrophic hard drive failure, I did have one scare with my Time Machine drive - but it wasn't something I can blame on Time Machine, not even indirectly. A few months ago, I plugged in the SimpleDrive to do a routine Time Machine run, and instead of chattering energetically as it normally does upon mounting, it just made some feeble and pathetic clicks and grunts, and after twenty or thirty seconds, the dreaded "this disk is unrecognizable by this computer" dialog sheet appeared.

This had never happened before in the two years or so that I'd been using this drive (which I like a bunch; it's sooo cool looking), and while two years is not an insignificant passage of time, the drive had only been used for backups on a periodic basis, so the number of hours was pretty low. Anyway, I tried removing the USB cable and re-plugging it several times to no avail.

I launched Disk Utility, which was able to see the drive and recognized it as a 500 MB unit, but no details as to content. The Verify and Repair buttons in Disk First Aid remained grayed out. Figuring that I had little to lose at this point (there was nothing important on the drive except for my Time Machine backups, which would be recoverable if I could get it working again, I attempted to erase and repartition the drive. That caused Disk Utility to crash. Twice. it wasn't even able to properly eject the disk, so I was obliged to unceremoniously cut the power and pull the cable out.

I tried plugging the drive into another PowerBook to see if the issue might have been with my workhorse 17" G4's system or possibly that overworked USB port, but it wouldn't mount on the second computer either.

This was all more than passing strange. While everything has to start sometime, there hadn't even been a hint of trouble the last time I had used the drive. However, it was beginning to seem probable that perhaps the hard drive had failed, which had only happened to me once before some years ago with a Fujitsu 2.5" hard drive in an external FireWire housing with less than 50 hours on it.

On the other hand, there was still a possibility that it was something else, so some more thorough diagnostics were in order. I decided that since the SimpleDrive is well out of warranty, I had little to lose in popping it open, which happily turned out to be quite easy, requiring the removal of just four easily accessed Philips machine screws and a bit of judicious prying to snap the case halves apart. Thumbs-up to the SimpleDrive folks for making the unit user-serviceable (so to speak) using ordinary tools. I love stuff that is easy to take apart (and put back together).

The Drive Works!

I removed the drive from the housing and connected it to my handy Daystar AnyDrive USB 2.0 Adapter, which has the happy facility of being able to connect virtually any 2.5", 3.5", or 5.25" ATA or SATA hard drive to Macs or PCs via USB.

I can't recommend this extremely useful and relatively inexpensive unit highly enough. Anyway, I connected the power supply and plugged the drive into the PowerBook, and it spun right up and mounted without hesitation or drama whatsoever.

Okay, it evidently wasn't the drive itself, which was a relief. Perhaps it was the cable. I reinstalled the hard drive in the SimpleDrive housing and connected it using the USB cable from my printer. Again, it powered up and mounted normally.

Was it the cable? Apparently not, since when I tried it again with its own cable, it was working fine now with that as well.

I was happy but perplexed. This sort of mysterious fault can make you tear your hair in frustration if it recurs. I did a Time Machine backup run, and that went completely smoothly as well.

Cause of the Problem

So what had been the problem? The thing to do in this sort of situation is to try to remember if any even slightly unusual occurrence comes to mind.

I don't as a rule pack the SimpleDrive around from place to place much, but I do keep it in a computer messenger bag for storage, and I now recalled that the day before I had picked up the case upside down, and the drive fell to the top with a noticeable thump. It wasn't a hard bump like being dropped on the floor, and it was inside a generously padded computer case, but then I further recalled that when I opened up the SimpleDrive housing, the large multi-pin ATA connector plug had popped loose a little too easily.

My assumption was initially that the plug got disconnected as I separated the case halves, but upon further reflection I settled on a provisional theory as to what probably happened: When the SimpleDrive shifted inside the computer messenger bag, the ATA connector, which I'm guessing had not been inserted securely at the factory, quite likely got jarred loose, resulting in only partial electrical contact and data transfer when I connected the drive to the computer.

The fact that the drive has performed flawlessly ever since - several months now - convinces me that is what happened. The drive got "fixed" when I reinstalled it in the housing and plugged the multi-pin connector in properly.

Just one of those weird glitches that crop up from time to time to keep life life from getting dull.

Link: Daystar AnyDrive USB 2.0 Adapter