Tag Archives: Hard Disk Failure

Time Machine – Not Such a Foolproof Solution

Last night we had the kind of problem that most computer users dread, the un-bootable computer. Beth had used the iMac earlier in the day without any problems, but when I tried to start the machine up, it stalled during the start-up process.

The next stage when you’ve got any sort of Mac problem related to booting is to reach for the OS X install DVD, and use that to start up Disk Utility – more often than not this will sort out a lot of problems, however not in this case. Having run through the verification and repair process it came up with a big red message warning that it couldn’t repair the disk.

No problem, I’ve got a regular back-up strategy – periodically backing up to an external hard drive using SuperDuper alongside using Time Machine and an associated Time Capsule. The last full backup I did was about a week ago, just before the OS X 10.5.5 update installed, however Time Machine has been quite happily running since then, so I opted to have the OS X install rebuild the drive and reload the data from the Time Machine.

Then the installer showed me a list of the contents of the Time Machine – with the most recent complete backup being just before the 10.5.5 update, complete with a message saying that “Only complete backups of Mac OS X appear in the list”. On the basis that Time Capsule has been running normally, there should be newer files on there, but the implication is that it hasn’t managed to complete a backup since then – thinking back over our usage over the past week or so that might be right as we’ve had a lot of short sessions.

Like most users I guess, we largely ignore the operation of Time Machine. The icon sits on the title bar, and periodically the Time Capsule springs into life. However the software is deliberately designed to be non intrusive, and will quite happily cope if you want to shut the machine down whilst it is working – it just shuts itself down as the machine shuts down and restarts again the next time the machine is turned on, my assumption being that it will just pick up where it has left off. However even over a week of short sessions, it should have picked up all the files.

A bit of a browse around the internet for problems after the 10.5.5 upgrade turned up this – looks like there have been problems, plus also some comments about the number of files changed in the update. Time Machine has a two stage process, first it goes through a prepare stage, which is when it builds a list of the changed files, then after that it goes into the backup where the status message showing the progress through the backup. It could be that during our relatively short sessions this week it is never actually getting beyond the preparation stage.

At this point I was rather glad that I kept the two part backup strategy, so I booted up using the backed up image of the main drive and was able to copy off our respective mail archives, which in my case would be the most annoying thing to lose, and then set the machine going overnight copying the clone of the boot drive back across to the iMac. Taking a look this morning however, the restore had again stalled part way through, leaving the boot drive with errors – so the drive was cleared down again, and I’m again copying the SuperDuper clone. Even if it works though, I’m not massively confident in the drive in the machine, so I also headed over to Mac Upgrades to pick up a new internal drive – picking one that hopefully will allow us a bit more room to grow at 500Gb rather than the 160Gb that is in the machine at the moment. Apple also have a step by step guide to a DIY upgrade which seems pretty straightforward.

So any thoughts at this point? Firstly, I’m really glad to have SuperDuper around – the clone of the drive it produces coupled with the ability of the iMac to boot itself from the backup image is fantastic – if it wasn’t for that it would needed to have been either another Mac and FireWire target disk mode, or alternatively just losing the weeks worth of e-mail that hadn’t been backed up. The other important thought is to keep an eye on Time Machine and in particular when it has last done a complete backup – almost certainly explicitly forcing it to do a complete backup after significant operating system upgrades. The bottom line though is always make sure you have a good backup strategy – you never know when you might need it.

As to what caused it – it’s all a bit of a mystery. It could just be that the drive itself has given up – the machine is a few years old now and gets pretty heavy use. The other odd thing is that looking at the multi-way adapter into which the machine is plugged in, the light indicating that the surge protection is working is no longer illuminated. I could confirm one way or the other if I had the OS X logs, but they are of course on the failed drive, so I guess we’ll never know…