What is the best way to back up data?

I’m an experienced user but I’ve never learned anything about back up strategy or implementation (other than from Schofield’s laws).

What’s the objective of backing up? What would be a good backup strategy? How would you implement it?

Also, why backup to compressed files? Why not make the backup an image of the source (same folder structure), which makes it much easier for the inexperienced user to retrieve a single file if needed? Chris

I tend to bang on about backups because of the horror stories that appear in my mailbox. The latest example: someone took a laptop in for repair – it had a Windows XP software problem – and got it back with a different hard drive: all his data had gone. Hence Schofield’s Second Law of Computing, which states that data doesn’t really exist unless you have at least two copies of it.

The main problem is that most people don’t make backups reliably, if ever. For consumers, the problems of what, when and how to back stuff up are less urgent. They’re certainly important to businesses, but businesses can pay experts to tell them the answers, or they can buy pre-packaged “solutions” of various sorts.

Unfortunately, there isn’t a single answer, because people have different amounts of different types of data, and different needs. At one extreme, some people need a fail-safe system where everything is backed up all the time, and they can restore their computer to its state at an earlier date and time. Others may not care if their PC works, they just want to be sure they have copies of irreplaceable family photos, or the PhD thesis they have almost but not quite finished.

Different files obviously have different values. As a rough guide, work out the replacement cost of your files and how much you would pay to replace them. For example, the audio files you ripped from your CDs are not worth much: you could rip them again, or buy digital tracks on Amazon. Your unfinished PhD thesis, blockbuster novel or genealogy database would be worth a lot more because of the time and effort it would take to recreate it from scratch. Old family photos might be impossible to replace, and you would pay a recovery company £500-£1,000 or so to get them back.

Backing up a PC

A full backup would enable you to restore your PC to a previous state without losing anything, or not much. This is what backup software aims to do, and this includes the programs provided with Windows and other operating systems. To save time and disk space, these timed backups – often daily but sometimes hourly – are “incremental”, which means only changes are recorded. To save disk space, the files are compressed: you can’t see the originals on the drive, though you can extract them.

It’s very easy to set up a full backup system, though ordinary users may run into problems when the program has filled all the available hard disk space. Some systems may quietly throw away old files to make room for new ones, which means you might not be able to rescue the file you deleted a month or a year ago. Windows 7 periodically creates new full backups, so you can use the “manage space” option in the Backup and Restore control panel to delete an old one.

Another approach to backing up a PC is to take a “disk image”. Instead of worrying about the files, you just copy the whole drive sector by sector. Most backup programs allow this, including the programs provided with Windows. The advantage is that you can simply copy the whole thing back to your PC – or “re-image the drive” – and get back to where you were.

When setting up a new PC, I grab an image that includes all the Windows updates, plus my standard programs and settings. This can save a lot of work if something goes wrong. It’s like the Windows recovery partition on your PC, but updated and decrapified. (See Cloning a Windows hard drive.)

However, disk images are not a very efficient use of storage space. How many copies of a terabyte drive are you going to keep? How out of date is the latest version?

Backing up files

One alternative is to sort your files into different directories and back them up in the most suitable way. Some data changes a lot and needs backing up regularly, particularly if you need to protect current work files. Some data doesn’t change very often, and not all of it is vital. This probably includes music and audio files, ebooks, movies etc. Of course, if you were a musician or a photographer, some of these might be vital work files.

As you know, when files are backed up in directories, you can see what you’re got, and it’s easy to retrieve a file if you’ve deleted it by accident.

Backup strategies

It’s a good idea to schedule incremental backups to an external hard drive or a network-attached (NAS) server. You can use the software that comes with Windows or, with a NAS, that comes with the NAS. But it’s worth considering more powerful programs such as Acronis True Image 2014.

You can also make separate backups of the less volatile data (music, movies, photos etc). These can be kept on a separate drive partition: many PCs have their hard drive divided into C and D for the operating system/programs and data respectively. If not, you can create a Data folder with subdirectories for your audio and video files etc.

Note that copying files from C to another partition does not provide a backup. If the hard drive fails or your PC is lost or stolen, you lose all the partitions on that drive. You must copy these files to an external hard drive or server, or to removable storage such as optical discs (CD-R, DVD or Blu-ray), USB thumbdrives, SD cards, or whatever.

Also note that if you move a lot of big files to an external hard drive or NAS either to save space or to share them, then you don’t have a backup. You may need a second EHD to back up the primary EHD or NAS.

You can use file synchronisation software to back up sets of files to an external hard drive. I use FreeFileSync but there are alternatives. You may also be able to find or write batch files to do the job. But there is a catch with mirroring drives: if you don’t notice that you have deleted a file or folder by accident, the sync program will delete it on the backup drive.

Multiple PC worlds

If you have several PCs to back up, it’s better to buy a NAS or set up a home server (you can use an old desktop PC) to centralise the process. When buying a NAS, check that the built in software can back up multiple PCs and, preferably, your other devices. (See: Which NAS should I buy to store files?) If you have from five to 25 PCs and business data to back up, consider buying Microsoft Windows Server 2012 R2 Essentials for about £300 on Amazon.co.uk. Like most NAS software, this now supports smartphones and tablets, including iPhones, iPads, and Android devices.

In the longer term, it should be possible to back up PCs and other devices to the cloud. At the moment, most people don’t have fast enough internet connections, and online storage space is too expensive. It’s easy enough to store, synchronise and/or share files in online drives such as Dropbox and Microsoft OneDrive, but these consumer-oriented services are not suitable for backing up terabytes of data. For backups, you need a different kind of service – one that doesn’t sync – such as CrashPlan, Carbonite or Mozy.

However, 3TB hard drives are cheap, reliable and (with USB 3) very fast, 4TB drives are improving and 8TB drives are on the way. The main question is whether you want each drive in its own external enclosure, or whether it’s better to have them in a 2-bay or 4-bay NAS.