ACRONIS Backup & Recovery 10 Server, Windows Guide de l'utilisateur télécharger pdf (Page 125)

Backups of different levels have different types:

 Last-level (in this case, level 4) backups are full;

 Backups of intermediate levels (2, 3) are differential;

 First-level (1) backups are incremental.

A cleanup mechanism ensures that only the most recent backups of each level are kept. Here is how

the archive looks on day 8, a day before creating a new full backup.

1 2 3 4 5 6 7 8

4 1 2 1 3 1 2 1

The scheme allows for efficient data storage: more backups accumulate toward the current time.

Having four backups, we could recover data as of today, yesterday, half a week, or a week ago.

Roll-back period

The number of days we can go back in the archive is different on different days. The minimum

number of days we are guaranteed to have is called the roll-back period.

The following table shows full backup and roll-back periods for schemes of various levels.

Number of

levels

Full backup

every

On different

days, can go

back

Roll-back

period

2 2 days 1 to 2 days 1 day

3 4 days 2 to 5 days 2 days

4 8 days 4 to 11 days 4 days

5 16 days 8 to 23 days 8 days

6 32 days 16 to 47 days 16 days

Adding a level doubles the full backup and roll-back periods.

To see why the number of recovery days varies, let us return to the previous example.

Here are the backups we have on day 12 (numbers in gray denote deleted backups).

1 2 3 4 5 6 7 8 9 10 11 12

4 1 2 1 3 1 2 1 4 1 2 1

A new level 3 differential backup has not yet been created, so the backup of day five is still stored.

Since it depends on the full backup of day one, that backup is available as well. This enables us to go

as far back as 11 days, which is the best-case scenario.

The following day, however, a new third-level differential backup is created, and the old full backup is

deleted.

1 2 3 4 5 6 7 8 9 10 11 12 13

4 1 2 1 3 1 2 1 4 1 2 1 3

This gives us only a four day recovery interval, which turns out to be the worst-case scenario.

On day 14, the interval is five days. It increases on subsequent days before decreasing again, and so

on.

1 2 ... 120 121 122 123 124 125 126 127 128 129 130 ... 216 217

Commentaires sur ces manuels

Pas de commentaire

ACRONIS Backup & Recovery 10 Server, Windows Guide de l'utilisateur Page 125

Commentaires sur ces manuels

Produits connexes et manuels pour Logiciel de sauvegarde et de récupération ACRONIS Backup & Recovery 10 Server, Windows