4 4 3 Beefalo:Media Strategy
SEP sesam media management provides simple and efficient management of a large number and different types of media. Among its powerful features are:
- 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 non-ambiguous 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. 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.
Media should be fully utilized and written on until the EOM (end of media). No entry for EOM is necessary – SEP sesam will request a new medium from the corresponding media pool automatically when the medium or tape is full.
When there is a single media pool linked to a media event or schedule, the GET_OLDEST policy is always applied. This preserves the data on the media for the longest possible time.
If the media event includes 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 or the backup will be blocked.
The GET_OLDEST strategy determines which medium is to be used next. Preference is given to media according to the following criteria:
- Media whose EOL has expired. (If a saveset is stored on tape, the EOL of all stored savesets must be expired.)
- The oldest medium – medium 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.
Blocked backups can be prevented by using SPARE pools. Spare pools are used by media events when media from the actual pool are inaccessible. A medium is moved from the compatible spare pool to the pool currently being accessed by the backup. From here, the spare media migrate to the working pools, resulting in a dynamic increase of media pool size, depending on the amount of data being backed up.
Unused media are inserted and kept for later use. For each type of drive, a compatible spare pool with free media should be created.
SPARE pools can be used to automatically insert new media into working media pools. The media are then migrated as necessary to the working pools on the production system.
The name of a spare pool starts with SPARE_.
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.
Archive adjustment makes a comparison between media in the loader carousel or magazine and the SEP sesam media archive database. It is mandatory whenever the contents of a loader carousel have been altered. Typically, it must be performed after inserting new media or used media that have not yet been registered (initialized) by SEP sesam.
Select the Automatic New Entry option to enter the new media automatically.
To start the adjustment using the GUI, select Main Selection -> Components -> Loader -> Archive Adjustment. For 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. When using 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. Media pool retention time is specified in days and defines how long the backed up data on media remains protected after the data is written to the medium. The retention time period starts with the date a saveset is written to the medium and lasts for the period defined by media pool's retention time. When the protection expires, SEP sesam can re-use the media for backups again.
SEP sesam allows you to adjust EOL for individual saveset (saveset EOL) or for all backup-related savesets (backup EOL).
As of v. 4.4.3 Grolar, modified EOL is recorded in main log.
- Saveset EOL
- This parameter is available under several properties views, for example, in the backup task properties or in the saveset properties (e.g., Components -> Data Store -> Properties -> tab Savesets -> Saveset EOL). It enables you to change EOL for each individual saveset, stored on the respective medium. You can extend or reduce its retention time. If the adjusted saveset is part of a backup chain, the whole chain is affected. See EOL-related backup chain dependencies.
|Each saveset that is stored on tape has its own EOL, but this does not represent the actual expiration date of the tape. The tape media EOL is the maximum EOL of all savesets stored on the same tape. Only when all of the savesets on tape have their EOL expired and the tape is no longer locked (write-protected), the entire tape is eligible for re-use.
The tape media EOL may also depend on savesets that are not stored on this tape. This is when the tape contains savesets that refer to FULL/DIFF/INCR savesets stored on other media or even data stores. For details, see What is dependency-based retention.
- Backup EOL
- The parameter Backup EOL (Components -> Data Store -> Properties -> tab Savesets -> Backup EOL) enables you to adjust EOL for all savesets containing the same data, including migrated and replicated savesets.
For example, adjusting EOL of a migrated saveset from the 2nd of December to the 22th of December results in changed EOL for all related backup data, i.e., original backup, replicated backup, as well as for all backups in a backup chain, if a saveset with adjusted EOL is a part of it.
|How SEP sesam manages failed backups depends on its version. As of v. ≥ 4.4.3 Beefalo V2, SEP sesam keeps the failed backup according to the media pool retention time together with the last successful backup or migration saveset. This is the default backup retention behavior and can be changed by modifying retention-related keys, as described in Customizing retention policy. These keys may not be supported in previous versions, where failed backups were deleted automatically after 3 days.|
- EOL-related backup chain dependencies
- You can extend or reduce EOL for a single saveset (Saveset EOL) or for backup-related saveset (Backup EOL), as described above. Keep in mind that increasing EOL of a DIFF or INCR saveset will result in increased EOL of all dependent backups (FULL and other DIFF and INCR) in order to retain the backup data. This keeps the backup chain readily available for restore. On the other hand, expiring EOL of the DIFF or INCR savesets results in purging and overwriting the complete backup chain!
|The storage space of each saveset can be re-used when the following conditions are met: