How Reliable is Your Backup?

Data backup is at best treated as a necessary evil and at worst, is something that is never even considered. But backing up your data is a very serious subject and cannot be ignored.

Gone are the days when companies held most of their data on paper stored in rows of filing cabinets. Now it’s mainly recorded on hard disk, possibly on different computers in various locations. These computers may be all networked, making all this information readily accessible through fast searching and data extracts. However, it’s no less vulnerable to loss and a hard disk failure with no backup available can mean catastrophe for your company.

Data Loss

All companies need to ask themselves what the effect of data loss will be. At best, if they have a recent and reliable backup copy, they can restore from that and then only need to re-input from the time of the copy; they may lose a few hours work at the most.

The worst case scenario is when mission-critical data is lost and there is no backup available. Rebuilding this data may be virtually impossible and the company’s very survival may be threatened as a result.

All companies need to have a proper backup strategy where data is copied frequently, verified for completeness and stored securely. The strategy also needs to include how the data is to be restored and in what circumstances.

How frequently you back up depends on how much data you input and the time you are prepared to spend re-entering lost data. Clearly, if you back up each day and a failure occurs immediately prior to the next backup, you have a full day’s data to re-input after restoring the files. If this is too much, you may need to take a security copy more frequently, possibly at lunchtime and the end of the day.

Although data transfer times have improved, a copy can still take a long time if there is a lot of data. However, you don’t need to back up the full content of your hard disks. All the programs can be re-installed and don’t need to be copied. Similarly, data that hasn’t changed needn’t be copied.

Incremental Backups

Many companies will do a full backup once a week and then daily incremental backups that only copy the data that has changed since the last backup. This shortens copy times and means that, in the event of a disk failure, data needs to be restored from the latest weekly copy and then the daily ones since then.

Any backup strategy needs to include not only what is copied and when, but where it is copied and stored. Do not copy the data to the same tape or disk each time. Not only does this shorten the media’s life, it also means you only have a single backup, which may be corrupt. Ideally, you need to be able to go back a further generation at least, so you need to have at least two weekly copies and separate daily backups.

Backup copies must also be stored in a different location entirely. If a fire destroys your computer, it is also likely to destroy any backup copies held at the same site, which rather defeats the objective of making them.

Companies that set up backup strategies often assume that the job is done. Copies are taken automatically at set times and the backup copies are stored securely away. But often no-one thinks to check that everything had worked as it should have done.

Each time a backup occurs, the backup log needs to be checked. If this shows the backup has failed, it must be re-run correctly to get a valid copy.

Companies also assume that, because the copy seems to have run successfully, the backup copies are correct. If they are not, this can result in a nasty shock when a data restore is necessary. You must periodically verify that backup data is being created correctly by doing a trial restore to an external hard drive or a different computer. This will reveal problems before they become critical.

Having a proper backup strategy and periodically checking its validity will reduce the risks to your company.