Why do we need to backup data?
Computers are becoming ever more reliable and data storage is highly reliable, however backup is still required for a number of reasons:
You might drop your phone down the toilet or the might be a fire in the office
Over time all data in storage devices suffers corruption so you need to have backups
If a user accidentally deletes data
You might want to rollback a database or program to a previous period of time.
You data might be deleted or encrypted by a third party who then go on to try and blackmail you into paying them money in return for your data back.
Backup Factors to consider
It is important that organizations have a plan in place for if their data gets deleted.
When creating a backup plan there are a number of factor to consider:
Where is the data going to be backed up to?
- Are you going to back the data up onsite, offsite or in the cloud?
- Are you going to back up the data to multiple locations?
What medium(s) are you going to back up the data to?
- Are you going to back up to….?
- DVD – to post to an offsite location and to redistribute
- HDD – fast and reliable with a fairly high capacity
- SSD – very fast but low capacity
- Tape Drive – Very high capacity but very slow to backup / restore
- Cloud – Multiple locations makes it reliable but not as secure
When are you going to perform backups?
- The backup might tie up network bandwidth so may be best to do in the evening
- Is there a specific event that the data should be backed up before (such as server upgrades)
How often will the data be backed up?
- Higher frequency means the backups are more current but it also increases storage requirements and network traffic usage
What data are you going to backup?
- Does all the data need backed up or are there certain files that are more important than others?
How is the backup going to happen?
- Is the process going to manual, semi automated or fully automated?
- How will you check if the backup is successful?
Who is responsible?
- Who is responsible for making sure the backups happen / are successful?
What is the procedure?
- What is the backup procedure?
- Where is it written down?
- What happens if somebody leaves the organization or is ill?
Full vs Incremental
Full vs Incremental Backups
A full backup is where all the data contained on a drive / location is backed up every single time. This has the advantage that if there is a problem then any of the backup images can be used to restore the lost data. If there was a hack within the last few days then an older backup image can be used that is hack-free.
A big disadvantage of full backups are the storage size of the backups, which will increase in size by the entire contents of the drive every single time you do a backup. Also if the data is being backed up off-site then the backup will be a huge drain on network resources.
Full backups are quite wasteful, especially if most of the data doesn’t change on a daily basis (as is the case with most websites or office server data)
A more sensible solution is to perform a full backup on a monthly basis and then in between each full backup perform an incremental backup daily. An incremental backup only backs up data that has either been added or changed since the last full backup. This compromise allows the advantages of daily backups but without the massive storage requirements issue.
Real World Examples
Real world examples of system failures due to backup problems
Past Paper Questions
June 16 Paper 13 Qn 3b