CREATE & MANAGE DATA
STORING YOUR DATA
Making back-ups of files is an essential element of data management. Regular back-ups protect against accidental or malicious data loss and can be used to restore originals if there is loss of data.
Accidental or malicious loss of data can be 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 precise back-up procedure to adopt depends on local circumstances, the perceived value of the data and the levels of risk considered appropriate for the circumstances. For many researchers, carrying out an informal risk analysis provides an indication of back-up needs.
Should you back up particular data files or back up 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 take responsibility only for your data files. If it cannot, you may wish to take full responsibility for your own 'system' back-ups. Where applicable this should include portable computers or devices, non-network computers and home-based computers.
Where data contain personal information, care should be taken to only create the minimal number of copies needed, e.g. a master file and one back-up copy.
Does your institution have a back-up policy?
Most universities have a back-up policy for data that are held on a university network space. You should check with your university about any strategies and policies in place. If you are not happy with the robustness of the solution you should maintain an independent back-up of critical files.
How often should you back up?
To reduce risk as far as possible, back-ups should be made after every change to data or at regular intervals. You can use an automated back-up process to back up frequently used and critical data files. Microsoft SyncToy is an easy-to-use method of synchronising files in different locations.
Which media should I use?
The choice of media on which to store back-up files depends on the quantity of files, type of data, and the preferred method of backing up. Examples include recordable CD/DVD, networked hard drive, removable hard drive or magnetic tape. If you are backing up many small data files on a daily basis, copying them to a recordable CD probably suffices but if you are making back-ups 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 should I back up in?
Back-ups of master copies should ideally be in file formats that are suitable for long-term digital preservation, that is open as opposed to proprietary formats.
Should I carry out incremental or differential back-ups?
Incremental back-ups consist of first making a copy of all relevant files, often the complete contents of a PC, then making incremental back-ups of the files which have altered since the last back-up. Removable media (CD/DVD) are recommended for this procedure.
For differential back-ups, a complete back-up is made first, and then back-ups are made of files changed or created since the first full back-up and not just since the last partial back-up. Fixed media, such as hard drives, are recommended for this method.
Whichever method is used, it is best not to overwrite old back-ups with new!
Where should I store my back-ups?
Depending on the form of back-up and the risks associated with data loss, it is most convenient to keep back-up 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.
Validation of back-up copies
It is important that you verify and validate back-up files regularly by fully restoring them to another location and comparing them with the original. Back-up copies can be checked for completeness and integrity, for example by checking the MD5 checksum value, file size and date.
How should I organise my back-ups?
If you are making your own back-ups on removable media, make sure they are well labelled and well organised. Without some management, achieving the ultimate aim of restoring lost data may prove difficult.