Can you recommend the best method to backup the My Documents folder on my computer in increments? I have both a USB key and USB external hard drive with copies of the My Documents folder which I manually make every week. Is there any software available which can backup any file that has been changed within a given period of time and does not touch anything else, as this would be both more time efficient and space efficient on the external storage devices. The computer is running Windows XP although I would also like to backup my Windows 7 laptop using the same method.

This is a very good question and you have already hinted at the type of backup that you would like to complete. Copying only data that has changed within a given period of time is known as an “incremental” backup. Before discussing this type of backup any further, and software that is capable of completing incremental backups, we need to talk about the various types of backups available so you can understand the implications of running incremental backups.

At the moment each week you are copying the entire contents of the My Documents folder to your external storage (USB flash drive/key and USB external hard drive). This is known as a “full” backup, as you are backing-up (copying) all data in the backup source (i.e. the My Documents folder on your computer) to the backup destination (the external storage device). While this does offer the best level of data protection, since you are backing up all of your data, it is not a very efficient method of backup because it is likely that a fair amount of data does not change on a weekly basis (such as documents which you need to keep, but do not regularly change). Therefore, each time you do a full backup you are re-copying data that has not changed. If you like to keep your backups for a period of time (for example, many organisations legally must retain their backups for several years) then you need a lot of backup storage to keep all of these full backups.

The second problem with only doing full backups is the time it takes to complete the backup. A fairly standard backup routine for a business is doing a daily backup of data, meaning that the backup runs every night so that any data changed during the day can be captured by that backup. Imagine that a business has multiple terabytes of data. Doing a full backup of that amount of data would take much longer than 12 hours overnight and therefore the backups would not complete during their dedicated backup “window” overnight (this is the maximum amount of time backups have to run before being suspended, as running a backup during business hours can significantly slow down the performance of IT systems such as file servers). Combined with the fact that you are likely backing-up a huge amount of information that has not changed in the last day this is incredibly inefficient. Therefore, there must be a better way to backup.

As it is simply not efficient or, in many cases, feasible to run full backups all the time there are two other mainstream types of backups: differential and incremental. A differential backup contains all the files that have changed since the last full backup. This means that if you run a weekly full backup on Sunday and then run differentials from Monday to Saturday you only need the full backup plus the daily differential of interest to restore data. However, this is also quite inefficient because each differential contains the data backed-up in the previous differential plus any changed data on that day. For example, the Thursday differential contains all files changed since the last full backup (Sunday) – so it would contain the Monday, Tuesday and Wednesday differentials plus any data changed on Thursday. That said, while it is inefficient it is convenient because you only need two backup sets to restore data – the full and the relevant differential.

Incremental is generally a more popular form of backup. This contains all the files that have changed since the last incremental backup (or if this is the first incremental since the full, it contains all the files that have changed since the last full). Continuing with our previous example, if we run a full on Sunday and then incrementals on Monday to Saturday, then to restore data you will need the full backup plus all the incrementals up to the day that you wish to restore. For example, if you want to restore something from the Thursday backup then you will need the Sunday full plus the incrementals from Monday through to Thursday (inclusive). This is much more space effective, since each incremental only stores the changed data from the previous incremental rather than a cumulation of the changed data from the last full. However, the downside of the incremental is that if one of the incrementals gets corrupted (or is somehow made unavailable, such as due to accidental deletion) then you cannot restore any data which requires that incremental backup (i.e. the backups from that day or in the future past that day). This is why most organisations run incrementals during the working week and then a full backup over the weekend – this means that if an incremental gets lost then the longest possible time the organisation cannot recover from backup is one week, as the full will restart generation of incremental backups again based upon that full backup.

This has been a fairly long-winded explanation of the different types of backups, but hopefully the discussion has provided you with more information so that an informed decision can be made about the type of backup that you wish to implement. For a home user it may not be necessary to do daily backups, so you may elect to do weekly incrementals and then a monthly full. That said, if you do work on the computer regularly and wish to have more frequent backups then you could elect for a daily incremental and weekly fulls. In this case the backups should not take very long, since it is unlikely that a large amount of data would have changed on an individual computer in the space of one day. In any case, I would recommend that you complete a full backup at least every month just in case something untoward happens to one of the incrementals which could prevent you from restoring any data which requires that incremental backup.

There is software built into Windows XP called NTBackup which facilitates this type of backup, and in Windows 7 this has been renamed to the Windows Backup and Restore Center. So I would encourage you to look at these options to see whether they meet your needs. The program built into Windows 7 is quite good, however the NTBackup software in Windows XP is not particularly user-friendly and is more geared towards advanced users, so you may be better off looking for a third-party product for the backups. In this case, it may be simpler just to purchase two copies of the software for both your Windows XP and Windows 7 machines so that you are running consistent backup software across both platforms (allowing you to configure both the same, so that you have a degree of standardisation).

There are plenty of different packages available to facilitate backups, and one product which I have had experience with in the past is Acronis True Image Home (www.acronis.com.au/homecomputing). While I have not used this software in a while, and the version which I reviewed is now several years old, it did prove to be a good product which meets the needs that you have described. You can find a full listing of features available in this product at www.acronis.com.au/homecomputing/products/trueimage/features.html . There is also a free trial of the software available on their website, if you wish to download and install this software to see whether it meets your needs.