Selecting a Backup method

The GFS backup method selected, determines how daily backups are performed. On the Method/Schedule tab of ARCserveIT's Backup Manager, you can select to use a five or seven-day rotation scheme consisting of full, incremental or differential backups. The following table outlines each option:

Method	Description
Full Backup Daily	A complete backup of every client in the set is performed.
Incremental	Only files that have changed since the last backup will be included in this backup.
Differential	ARCserveIT compares the source file's modification date with that of the last full backup. Only files that have been changed since that date are included.

Which method should you use?

Depending on your needs, examine each method and decide which is best for your company. For example, a full backup is easiest to restore, since your most recent data is on one media. But full backups take longer to perform than incremental or differential, and if you have a large amount of data to be backed up, it may be unreasonable to perform full backups every day. Some of the questions you should be asking yourself when deciding upon a backup strategy are:

• How much data gets backed up?
• What percentage of data in my set changes day-to-day?
• How long do I want the backup to take?
• If I have to recover files, how long do I want to spend restoring?

Use Incremental for backups that take less time and need less media

If you have large amounts of data to be backed up every day, but your restore needs are not as pressing, choosing Incremental backups daily may be your best solution.

Incremental backups only include files that have changed since the last backup, and in general is considered the quickest method for backing up. However, if you need to recover a client, you will need the last full backup, and all incremental backups after that. For example, if you perform full backups on Monday, and incremental backups Tuesday through Friday, and on Friday you need to restore a host, you will need Monday's full backup and Tuesday through Thursday's incremental backups to recover all the files for that host.

Differential may be for you if you want to restore files quickly, using less media

On the other hand, if you want to quickly recover files from only one or two media, and you do not care as much about how long the backup takes, choose the differential method.

Using this method, only the files which have changed since the last full backup job are backed up.

Since differential backup jobs are based on the file's modification date since the last backup, the files that were backed up in the last differential job are backed up again.

Using the same example as above, on Friday you would need Monday's full backup, and Thursday's differential backup media to recover all the files for that host. This is because Tuesday's differential media contains files that have changed since Monday's backup, Wednesday's differential media contains files that have changed since Monday's backup (thus, all the files from Tuesday's media will also be on Wednesday's media), and so forth. Your media requirements increase the further you get from the last full backup.