5 1 0:Backup Chain Dependencies

Overview

You can use the saveset tree view in the GUI to determine dependencies and EOL of an FDI backup chain. You should use this overview before you manually change the EOL parameter to avoid breaking the backup chain.

What are backup chain dependencies

A backup chain consists of full, differential and incremental backups. Running respective backup tasks creates a backup chain on your backup storage consisting of a full backup, followed by differential and incremental backups, and, additionally, a backup metadata file. Some INCR backups use Changed Block Tracking (CBT), an incremental backup technology for virtual machines that creates faster and smaller backups.

An FDI backup chain can contain any number of backups that each depend on other backups in the chain and can also depend on another backup in the number of backups. A backup chain can contain the first (primary) backup and one or more dependent backups, such as migrated and replicated backups.

• A primary backup can be a backup that does not require any other backups for a successful data restore. Thus, a primary backup can be a complete backup, but a dependent backup may require additional backups for a successful data restore as it may depend on the additional backups.
• For example, for INCR backups all previous savesets (FULL, DIFF and INCR) must be present for a successful restore.
• If retention time is considered only from the perspective of an individual backup, it can ensure restorability of data only for that particular backup.
• To enable full recovery of the data backed up in the backup chain, all dependent backup savesets are tracked and their retention time is managed according to their dependencies.

Dependent backups are also classified by the respective depth of the dependent backups in the backup chain. The respective depth can be a measure of how many backups are required to complete the restore of a system, e.g. a VM, to a predetermined state.

SEP sesam provides the saveset tree view to determine dependencies and EOL of an FDI backup chain. This view shows a data structure that relates savesets to their dependencies.

Note

To ensure the recoverability of the entire backup chain and protect against data loss, SEP sesam provides automatic EOL (retention) management based on the dependencies of the backup chain. The rules for the automatically adjusted retention time are described in Automatic Retention (EOL) Management. You can also manually adjust the EOL of your data, as described in Changing Retention (EOL). Since long backup chains are inefficient and more vulnerable if something goes wrong because the backups in the chain depend on each other, and because they can simply become too long to restore (no more storage available, takes too long), SEP AG strongly recommends setting up regular FULL backups to avoid such problems, and setting the limit to up to 100 incremental backups.

Checking the dependencies of the saveset tree

Checking the saveset tree summary provides immediate information about the location and status of the available savesets for restore. By checking the summary, e.g., availability 5, you can look for savesets that are not readily available and then migrate them to enable mount and selective restore.

The saveset tree displays details of a saveset along with potentially dependent savesets that belong to the same backup chain. The saveset details are read-only and are intended to provide insight into the backup recoverability.

You can open the saveset tree view by double-clicking the selected backup in the backup list:

1. From Main Selection -> Job State -> Backups or from Main Selection -> Monitoring -> Last Backup State, double-click the selected backup.
2. In the backup task properties window, open the tab Savesets.

In the saveset tree, all savesets belonging to the same backup chain are displayed with the following details:

saveset

SEP sesam unique identifier assigned to a saveset.

starttime

The time when the backup was started.

level

The backup level used for the saveset: F (FULL), D (DIFF), I (INCR), or C (COPY).

More detailed information is displayed for each saveset:

pool

The media pool to which the saveset belongs.

EOL

The time when the saveset's protection expires. For details, see Rules for the automatically adjusted retention time.

avail

The priority number, based on the location of the savesets. It is useful for identifying savesets that are readily available for restore. Example: A saveset in the media pool DAY (data store) is migrated to another pool DeDup and then migrated to a tape. The tape will have the lowest avail(ability)/priority as it is not readily available for restore. Also check the Availability in the Status at the bottom of the tree view, which is calculated from the availability of all the savesets displayed. See Availability below for details.

reason

Explains the above availability (avail) of individual savesets for restore. The following information shows the relationship between location and avail/prio. Priority is assigned numerically, with 1 being the lowest priority and 6 (or 7 if called with a specific pool) being the highest priority.

TAPE_SINGLE = 0
TAPE_NOT_IN_LOADER = 1
DISK_OFFLINE = 2
TAPE_ONLINE = 3
DISK_HARD = 4
DISK_STORE_CLONE = 5 
DISK_STORE = 6 
REQUESTED_POOL = 7 (shown if called with a specific pool, e.g., all savesets on pool DAY and saveset_tree was called with target pool DAY)

drivegroup

Displays the name of the drive group related to the saveset's media pool.

drives

The number of the drive used for the backup.

labels

Displays an internal label of a saveset (a media pool name and a 5-digit number), a potential barcode, prio (numerical representation of availability, see above item), and a comment.

status

Displays the summary of the saveset availability – status, availability message, and a numerical representation. For example, as soon as 1 saveset is migrated to another pool and deleted from the original pool, the availability is lowered.

See also

Automatic Retention (EOL) Management – Changing Retention (EOL) – Backup Strategy Best Practices – Tape Management

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