Most of us have old family photo albums and other personal records which might go back many decades – possibly even to the 1800s. Passed down from generation to generation, they give us insight into who our ancestors were, where they lived, and the events that shaped their lives. They are of more general value too in helping maintain a balanced history of our societies and cultures.

Today’s records are both richer and more copious. We surely don’t want to keep every digital image which we take, every movie clip which we shoot, and every email which we exchange with friends and family, but most of us want to retain a selection.

There are also records which we have to keep: work projects which we may need to refer back to, contractual and legal matters, and of course our tax and related financial records.

For a while, there is no problem keeping them on our Macs, now that capacious storage is so relatively cheap. A few metres from this Mac is my original IBM PC XT, with its 10 MB hard disk: back in the mid 1980s, storage was much more limited, and you had to keep archiving old documents from your hard drive, or you quickly ran out of space.

Archiving is distinct from backing up. When you back up your hard drive, you are making copies of changed files which you intend keeping on your working storage (hard drive, SSD, or Fusion Drive) and in your backup. When you archive, your aim is to put those documents into permanent storage, so that you can (eventually) remove them from your working storage. You may still keep a copy to hand, for example old family photos, but in time those will get whittled down, leaving the complete collection in your archives.

I have already written about the importance of choosing archival file formats. Here I will consider the storage media which can be used for your archives.

Old hard disks

At the moment, many of us use hard disks to store our archives, but don’t really create proper archives at all. Periodically I replace my Mac, its hard drive, or the drive(s) used for Time Machine backups. Instead of disposing of those hard drives, I put them on one side, and can then return to them in the future when I need.

This seems even better than making proper archives, because it keeps everything, but actually that is a major disadvantage. When you do want to find an old project, you may struggle to locate the right drive, and finding it on that drive may not be easy either. Because everything is archived, the mass of transient dross will get in your way when you try to access those archives.

The most serious issue, though, is with the hard disk as an archival medium. When in use, hard drives tend to last fairly reliably until their warranty runs out – the manufacturers engineer them to. Once out of warranty, failure rates start to climb higher, and after another couple of years or so, most drives have died.

Because archived hard disks are not in use, in theory they should not be using up ‘life’ when in storage. This would be true if they were not mechanical: no matter how carefully you might store them, some of their components will continue to age even though they are not in use. Data are recorded on their platters in fine magnetic particles, and it is well known that that recording surface degrades over time, and individual bits of data slowly corrupt: bit rot.

I have not been able to find any good real-world measurements made on stored hard drives, but most drive engineers suggest that they are likely to remain reliable for up to around ten years when stored in good conditions. That means away from magnetic fields, in a dark, cool, and dry place, sealed in conductive plastic bags. If you try to use hard disks for longer term storage, then you are likely to find more extensive data corruption, and it is possible that the whole drive will fail.

Other magnetic media

Many networks and individual systems used to back up to other magnetic storage media, such as tape and magneto-optical disks. Although these can have quite impressive capacities, they are already well on the decline, and were never known for their longevity. Even if you have one still, avoid using it for anything of importance.

Optical disks

CD-R, DVD-R and most recently BD-R (Blu-ray data) disks have been hugely popular, but their reputation for longevity took a knock a few years ago when there were reports of some disks suffering failure very early. Disk manufacturers are now quick to distance themselves from those problems, and several now claim that their archival quality media – not the ordinary everyday products – are good for “up to 100 years”, or even more.

This may sound a bit like an ISP’s promise of ‘up to 100 mbps’ which turns out to be a reliable 6 mbps, but the problems in specifying media life are far greater. You could buy the most expensive archival products, leave them in the sun for a few days, and find them unusable: with optical media, so much depends on how they are stored. But there is little doubt that, kept in dark, cool and dry conditions, archival quality optical media should last longer than any other medium currently available to you and me.

Archival grade DVD-R disks should cost around £1.50 each, to which you should add individual jewel cases or an archival storage system.

Blu-ray BD-R and higher capacity variants are not currently as well supported by disk manufacturers. Given that greatest concerns over longevity are now with BD-R format, and its lower market share, I would suggest that you do not use Blu-ray formats for archiving for the time being. This is a shame, as they offer 25, 50 and even 100 GB storage on single disks, provided that your Blu-ray recorder is suitably equipped. Whether you will be able to read BD-R disks in fifty or a hundred years time, and whether current media will last that long, is still an open question.

Workflow

The only way to determine whether files or folders are ready for archiving is for you to make that decision. Unlike backing up, you cannot leave even very smart software to decide for you. A good system is to create a folder in ~/Documents called ForArchive, and when you get a moment, to start loading it up. Once there is enough to write one or more DVD-R disks, use the Finder or a product such as Toast Titanium to write the contents to an archival DVD-R disk, put it in a jewel case, and store it safely.

If you want to be really well-prepared, write two copies, and send one to your off-site data store.

Although you will undoubtedly take care to label the jewel case (not the disk), using good cartridge paper (no adhesives which could accelerate deterioration in the disk), bear in mind that it might be your descendants who have to try to fathom out what is on there. Before burning the disk, it is worth taking a few moments to make a text file which explains what each folder contains in a bit more detail, a Read Me First file to sit at the top level of the disk to help anyone trying to access it.

If you are a creative, keeping records like this is hugely important for yourself and anyone in the future who may be interested in your work. Otherwise it will be ephemeral, and once you’re gone, it will vanish into the great bit bucket in the sky.