4 4 3 Beefalo:Media Strategy
SEP sesam media management provides simple and efficient management of a large number and different types of media. Its powerful features include:
- Efficient management of large sets of media.
- Protection against accidental overwrites.
- Spare pools prevent failed backups due to missing media.
- Recording and tracking of all media and their status: used capacity, EOL, user-defined write protection, etc.
- Barcode support on loaders.
Media used by SEP sesam are administered in media pools using unique labels. The labels consist of the pool name and a five-digit number assigned by SEP sesam within the pool. For this reason, a media pool name may never end with five (5) digits.
- Media pools are the basis for building a backup strategy. Each media pool represents a set of media designated for a specific purpose. The configuration of a media pool differs depending on whether you are configuring media pools for tape media or for data store (for backup to disk storage).
- In the GUI, a new media pool is created under Main Selection -> Components -> Media Pools -> New Media Pool. For details, see Configuring a Media Pool.
A SPARE pool is a media pool that you can configure to allow sharing of spare media across media pools to prevent blocked backups. Spare pools are used by media events when media from the actual pool cannot be accessed. Spare media are automatically moved from the compatible spare pool to the pool currently being accessed by the backup, eliminating the need for administrator intervention when media is not available. Migration of spare media to the working pools results in a dynamic increase of the media pool size, depending on the amount of data being backed up. The use of spare pools is optional.
- Unused media are inserted and kept for later use. A compatible spare pool of free media should be created for each drive type.
- SPARE pools can be used to automatically insert new media into working media pools. The media are then migrated to the working pools on the production system as needed.
- The name of a spare pool must begin with SPARE_. For details, see Configuring a Media Pool – Spare Pool. For more information on tape management operations, see Tape Management.
Media should be fully utilized and written to until EOM (End of Media). SEP sesam automatically requests a new tape from the corresponding media pool automatically when the tape is full.
Media utilization can be regulated by:
- Definition of the media pool retention time.
- Setting write-protection in a media archive.
- Media events in the SEPuler.
- Modifying the locking date of media in an archive to exceed the EOL and executing a media event.
Media selection is triggered by setting events that execute media selection strategies, reinitialize media and prepare media for scheduled backups.
A media event can be a user-defined event or an internal event created by SEP sesam. For example, if the specified media are not available at the start of a backup or if EOM (End of Media) is reached during data transfer, SEP sesam creates an internal media event that determines the next media for the backup.
User-defined media events are configured in the GUI and can be any of the following:
- initialization (a process that prepares the backup media for use with SEP sesam)
- readability check (a process that checks the readability of the backup data)
- close tape (a process that marks the tape as full and closes it so that no more data can be stored on it)
- archive adjustment (a process that scans the media in the selected loader and updates the SEP sesam information about the media status; see Archive adjustment section below for details)
If the media event contains a specific label, the system will attempt to find it and load it into a drive. The autoloader magazine must be accessible to SEP sesam, otherwise the backup will be blocked.
The GET_OLDEST strategy determines which media to use next. If a single media pool is associated with a media event or schedule,, the GET_OLDEST policy is always used. This preserves the data on the media for as long as possible.
Media are prioritized according to the following criteria:
- Media whose EOL has expired. (If a saveset is stored on tape, the EOL of all stored savesets must have expired.)
- The oldest media – media with the oldest locked until (is backup day+ media EOL) date in the media pool.
- Media that is not write-protected (locked).
For more details on protecting and reusing media, see below section Savesets Protection: Retention time and EOL.
Archive adjustment is used to make a comparison between media in the loader (tape library) and the SEP sesam media archive database, and performs database synchronization with the selected loader by updating the database with the latest inventory information of the scanned device. It is mandatory and must be performed whenever new media or used media that have not yet been registered (initialized) by SEP sesam are inserted to identify unrecognized tapes.
You can perform archive adjustment manually (Main Selection -> Components -> Loader -> Archive Adjustment ) or create a special media event for it and schedule it to run automatically at specified intervals. For more details, see Setting up Archive Adjustment.
|When selecting the option Archive Adjustment, make sure that the autoloader being realigned is selected in the GUI window, i.e. that the target device is at the top of the adjustment task. If you use the command line, the task must include the name of the target autoloader or tape device.|
Savesets protection: Retention time and EOL
When configuring SEP sesam environment, you set up media pools and define the retention time. The media pool retention time is specified in days and defines how long the backed up data remains protected after it has been written to the media. This is called the expiration date of the saveset - EOL (End of Lifetime). The retention period starts on the day a saveset is written to the media and lasts for the period defined by the media pool retention time. When the protection expires, SEP sesam can re-use the media for backups again.
The EOL property can be managed for three object types (as described in detail in Automatic retention management - EOL types):
- Saveset EOL
- The expiration date for a single saveset.
- Backup EOL
- The expiration date for all data belonging to the same backup, including migrated and replicated savesets.
- Media EOL
- The time until which backed up data on tape media remains protected. It refers only to tape media and is based on the longest EOL of all different savesets stored on tape.
If a saveset is part of a backup chain, its EOL follows the rules of dependency-based retention. When retention is considered only from the perspective of an individual backup, it can ensure data restorability only for that particular backup. To enable complete restore of data backed up in the backup chain, SEP sesam maintains control over the dependencies between backup savesets and provides six rules for dependency-based automatic retention. For more information, see Automatic Retention (EOL) Management.
The EOL parameter is available in several views, for example, in the Backup task properties or the Saveset properties for Backup EOL and Saveset EOL (Components -> Data Stores -> double-click the selected data store to open the properties -> tab Savesets: columns Backup EOL and Saveset EOL) or for the (tape) Media EOL in Components -> Media -> select one or more tapes -> right-click and select Change Media EOL. For more information, see Changing Retention (EOL).
|The modified EOL is also recorded in the main log and can be generated for audit trail purposes, see Audit Logging.|
The storage space of a saveset can be re-used when the following conditions are met:
- Its EOL has expired. (If a saveset is stored on tape, the EOL of all stored savesets must have expired.)
- If a saveset is stored on tape, it must not be write-protected (locked).
- Typically, there must be no other savesets that depend on this saveset. You can override this condition by explicitly allowing the EOL for the entire backup chain to expire, thus deleting backup data on all related savesets.
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