What would you do if you lost:
These are just a few (important) examples of what we keep on our hard drives and take for granted that they will be there when we next start up the computer. There are several ways that you can lose data:
The list could go on. What is important is that you protect the information that you have.
Ideally, data should be backed up into a haerarchical structure. The ideal structure is that there is a separate store for each of the following
With this system you have the ability to go back to files in small steps for a week, slightly bigger steps for a month, and large steps for a quarter.
It's important that all data can be backed up and restored - preferably using a single backup object. Once it spans 2 tapes / cd, the chances of a backup completing decreases dramatically
It must be scheduled - so that it happens when no-one is trying to use the systems (otherwise it will slow people down, and they will bypass the backup) and so that is happens whatever - it does not rely on someone taking an action.
Ideally the backup will be verified / restored to a server to ensure that the data is there, that it can be recovered, and that staff have the skills to do so in the event of a problem. This should happen before it is needed!
If the backup object is portable then on a regular basis the backup can be taken off site and stored in a safe location. In a (eg) fire, the fact that you've taken backup religiously is irrelavent if the backup tape has burnt aswell.
Some sort of protection on the backup object is a good idea as it means that in the event that it is lost, the data is of no use to anyone else.
There are a number of ways that this can be done effectively. They all have their pros and cons.
This is the classic commercial solution to backup. It scores highly on every requirement. The only down side is that the costs for equipment and tapes are high.
Many work systems will back up to a server. This is effective when the server is then backed up. If not then it presents problems with the data being at risk during the copy process, and does not provide a haerarchical backup
Suitable for small amounts of data. Doesn't give a structured backup.
This is a realtively cheap and easy way to backup a reasonable amount of data. If the backup spans more than 1 CD or DVD then the backup will become unreliable as it needs a human intervention to insert the next CD at the appropriate time.
Using a set of removable hard drives is an effective way to backup data - especially if you are replicating the tape drive scenario with hard disks instead of tapes. If you only have one removeable disks then your data is at risk whenever you are performing the backup, whenever the disk is in the machine. Also, many cheaper drive caddies mean that you have to power off the computer to plug in and remove the drive.
This means having two (or more) hard disks that functiln as one. If one fails then the other keeps the system going till the broken hard disk is replaced. Essential if you want a resillient data store or web server, but not really a backup solution. It only protcts you against hard disk failure.
A small amount of data can be copied to a remote location across your internet connection. This is a good idea for essential data - things like critical databases, accounts data etc. It is not practical for large volumes - like mailboxes or correspondence files.