Data backup

Making backups of files ensures that original data files can be restored from backup copies, should originals get damaged or go missing due to:

  • hardware faults or failure
  • software or media faults
  • virus infection or malicious hacking
  • power failure
  • human errors by changing or deleting files

Choosing a backup strategy depends on local circumstances, the value of the data, and the levels of risk appropriate for the circumstances. A risk analysis helps define backup needs.

Back up particular data files or the entire system?

What will you need to restore in the event of data loss? If your institution can restore your system, then you may wish to only take responsibility for your data files. If it cannot, you may wish to take full responsibility for your own 'system' backups. This should include portable computers or devices, non-network computers and home-based computers.

What if files contain personal data?

Where data contains personal information, take care to only create the minimal number of copies needed, e.g. a master file and one backup copy, and to encrypt the data.

Has your institution a backup policy?

Many universities and research institutions have a backup policy for data that are held on institutional servers. If you are not happy with the robustness of the solution, maintain an independent backup of critical files.

How often to back up?

To reduce risk as far as possible, backups should be made after every change to data, or at regular intervals. You can use an automated backup process to back up frequently used and critical data files.

Which tools could I use for automating backing up?

Microsoft’s Windows operating system now comes preinstalled with the ability to backup filesMicrosoft SyncToy is an easy-to-use method of synchronising files in different locations. Apple Mac’s come equipped with Time Machine which can make automatic backups at regular intervals.

Which media to use?

The choice of media on which to store backup files depends on the quantity of files, type of data and the preferred method of backing up. If you are backing up many small data files on a daily basis, copying them to a CD/DVD probably suffices, but if you are making backups of very large quantities of data from a networked hard drive, a removable hard drive or even magnetic tape is probably more convenient.

What file formats to use?

Backups of master copies should ideally be in file formats that are suitable for long-term digital preservation, i.e. open or standard formats as opposed to proprietary ones.

Incremental or differential backups?

Incremental backups consist of first making a copy of all relevant files, often the complete contents of a PC, then making incremental backups of the files which have altered since the last backup. Removable media (CD/DVD) are recommended for this procedure.

For differential backups, first make a complete backup, then make backups of files changed or created since the first full backup (and not just since the last partial backup). Fixed media, such as hard drives, are recommended for this method.

Whichever method is used, it is best not to overwrite old backups with new ones!

How to organise backups?

If you are making your own backups on removable media, make sure they are well labelled and organised. It is important that you verify and validate backup files regularly by fully restoring them to another location and comparing them with the original. Backup copies can be checked for completeness and integrity, for example by checking the checksum value, file size and date.

Where to store backups?

Depending on the form of backup and the risks associated with data loss, it is most convenient to keep backup files on a networked hard drive. For critical data, which are not available elsewhere, we would recommend that you adopt offline storage on recordable CD/DVD, removable hard drive or magnetic tape. Physical media can be safely stored in another location. Most manufacturers provide recommendations for the best storage conditions of physical media.

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