Master/Incremental Backups
There are two main reasons for using incremental backups:
- They take less time which reduces downtime.
- There is too much data to fit on one tape.
| Master Backup | This will transfer ALL information from the hard disk to the tape. |
|---|---|
| Incremental | This transfers only the files that have CHANGED since the last master backup. e.g. |
|
Sunday Master backup All Data Monday Incremental Files changed since Sunday Tuesday Incremental Files changed since Sunday Wednesday Incremental FIles changes since Sunday etc. etc. |
Incremental backups will take a lot less time to run which can help is you are doing manual backup's at say lunchtime. As the system is transferring less the backup time is a lot shorter. On my office machine a full master backup takes 37 mins (700Mb of data), simulating a practice situation and running an incremental backup this drops to 6 mins (161Mb), a saving of in my case about half an hour.
These days backup devices are much faster >100Mb/sec, the speed issue only comes into play when you have a slow tape drive or you want a quick backup. One good reason for this is if you have a clash of times with a validation run. It is possible to switch just one day's backup e.g. Sunday to incremental if your automatic validation takes a period of time.
Usually Edge is configured to run a full Master backup overnight, however, the situation may arise where the amount of data being transferred to the tape exceeds the capacity of that tape. In this situation the backup will stop and you are asked to enter a new tape. The problem is this is happening in 'the background' so you don't see the Insert new volume question. The following nights backup will fail.
In this situation you should consider doing Incremental backups nightly and a master backup weekly/monthly.
You will still need to do Master backups especially if any system changes are made e.g. new hardware, new software etc. Try to do a master backup at least once a month. The Master backup tapes MUST be kept separate from the daily ones.
It the event of needing to restore files then the procedure will be
Restore the last Incremental backup
So if anything happens to the master tape then you will have difficulties as only part of the data will be restored.
Keep the master tapes safe.
It is a good idea to have three master tapes used in rotation and say 5 daily tapes used in rotation.