Computers still oversimplify the real world. Their simple logical true-false, or binary 1-0, categorisation just doesn’t do life justice.

On Friday night, one of the four hard drives in my Promise RAID 5 system died. Inevitably, it occurred just as I was trying to prepare some screenshots for publication, as someone had sent me an iMessage, and there were a few other things going on at that same time. There was no S.M.A.R.T. or other warning: one moment the lights were all blue for go, the next, one was burning red for dead. I didn’t even have the time or presence of mind to run through the Dead Parrot Sketch from Monty Python.

As it is configured in RAID 5 format, my Time Machine backups which are stored there should still be OK. In the words of the reassuring article, “upon failure of a single drive, subsequent reads can be calculated from the distributed parity such that no data is lost.” I have ordered a replacement drive, which might get here in time for Christmas (so much for promised next-day delivery), and once it is installed I hope the RAID system will rebuild correctly.

But for now, no more Time Machine backups, and the Promise system is firmly shut down. A second drive glitch and four years of backups go forever to the Great Bit Bucket in the sky.

My fallback is to back up my most critical files to iCloud. But with a bit less than 5 GB available there, and a typical rural semi-broadband connection, I am not going to squeeze much of the 360 GB of my Documents folder onto my iCloud Drive. This is where that very human skill of judgement comes in: I cannot work like Time Machine and just back everything up, but have to determine what needs to go on my iCloud Drive in terms of its importance.

I first broached the issue of importance and computer file systems over eight years ago, in an editorial piece which I wrote for MacUser, and updated here. Since then the use of metadata in OS X has flourished, we can search by Finder tags, and more, but our Macs and iOS devices still know nothing of the importance of anything.

Time Machine will back files up, or not: black or white, true or false, 1 or 0. I cannot tell it what is most important, so it treats ephemeral notes and property lists exactly the same as critical work in progress.

OS X does now treat some of its own files with special importance: these are not just protected by standard POSIX permissions, but by the SIP mechanism introduced in El Capitan. Try tampering with the contents of most of the hidden top-level folders, such as /bin or /sbin, or the System folder itself, and you will discover how defensive it has become. But again, it is all or nothing, there’s no option to add your own folders to its watchlist.

File systems are a bit like precocious three-year-olds: they can show your files in alphabetical order, or reverse, according to their size, or the date last modified. Ask them to show you what is important, and they’ll just go and grab their favourite toy. Yet even the most disorganised adult has some system of discriminating what things are most important. Otherwise they couldn’t keep losing them.