Archive:The Backup 4.0
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Automatic backups are monitored and initiated by the SEPuler. Data specified in task for backups are copied to saveset on the pre-selected media.
To speed up and simplify the restore of desired data SEP sesam creates additional listings and media segmentation data. Doing so shortens recovery time.
The SysAdm user defines which data in his network should be backed up and sets the backup event schedule. Decisions must be made during the task configuration regarding media, media pools and backup type (full, differential, incremental). The SysAdm uses this pre-determined configuration to select and organize backup tasks, schedules and events. If desired PRE- and POST-interface commands must be configured at this juncture, as well.
Full-, Diff-, Inc-, Copy-Backup
The Full-Backup copies all the files of the source defined in the task. When doing a restore this version of the files can be restored easily by copying it back from the medium but this may in come cases be a very large amount of data to. The archive bits are not deleted on Windows systems. Information about the status of that backup for diff- and inc-backups that are based on it is stored in the SEP sesam database. If you want to force-reset of the archive bits you can do so via the backup options by entering -o clear_archive.
A Diff-Backup (differential) saves only those files that were altered since the last full backup (of the same task). This can drastically shorten the backup time. To restore the whole data source, the saveset of the full backup has to be copied back first before the saveset of the diff-backup can be copied. This means that two steps are necessary. This however is detected and performed by SEP sesam's generation restore.
An Inc-Backup (incremental) saves only those fields that were altered since the last backup of the same task. This way generally creates the smallest amount of data. In order to restore the whole data source, first the saveset of the last full backup as well as all inc-backups have to be copied back. Therefore, depending on your backup strategy, several steps are necessary which are however performed by SEP sesam automatically. A combination of full backups onto tape drives and diff- or inc-backups onto virtual disk media is a common method.
A Copy-Backup is a full backup that has no influence on following diff- and inc-backups. For the treatment of archive bit see full backup above. This type is usually used for additional full backups, e.g. monthly backups, or backups for archiving, i.e. removal from storage.
Backup with VSS (Volume Shadow Service) on Windows
With the Volume Shadow Copy Service (VSS) opened files can be consistently backed up under Windows. Thereto by Windows a non-persistent snapshot (shadow) is taken of the volumes and then backed up.
In the saveset the data is stored with original location, e.g. "C:\".
The total amount of VSS snaphosts is restricted to oper systems:
- under XP only one set (with some volumes) is allowed,
- other oper systems allow up to 64 sets.
If the restricted total amount of created volumes will be exceeded then a VSS backup fails. The total amount includes VSS snapshots which may be created otherwise!
As VSS uses the Copy-on-Write method only the amount of space for data which is changed during backup is needed as additional space during backup. The non-persistent snapshot disappears after the backup and does not occupy a volume identifier. Differential and incremental back ups are processed on the shadow. The restore is unchanged due to saveset has stored original pathes.
- "How Volume Shadow Copy Service Works" http://technet.microsoft.com/en-us/library/cc785914.aspx
- "Shadow Copy" http://en.wikipedia.org/wiki/Shadow_Copy
A description using SEPsesam Pre-/Post-Interface for SEPsesam Version 3.0 is located under SEP sesam Volume Shadow Copy Service (VSS) for Windows via Pre/Post.
- Client operating system: Windows XP, 2003, 2008
- Sesam Server from version 22.214.171.124
- Sesam Client from version 126.96.36.199
Activation/Deactivation of the VSS Shadow Backup
When creating a new backup task you will see the option Backup with VSS. This box is checked by default and can be unchecked if necessary.
Sesam supports parallel i.e. simultaneous backup for several data sources onto one drive. This is called Sesam Multiplex Stream (SMS).
Modern tape drive manufacturers have continued to dramatically increase device performance and capacity. Few of today's backup software products are able to fully utilize the new functionality to its greatest advantage. The drive is often in a 'stopped' or waiting mode for data from the backup source. SEP sesam is one of the few backup software products that can be used for receiving data from other backup sources. Sesam Multiplex Stream now offers up to 64 channels on a single drive; each channel can serve one backup source.
Data of the different streams are distributed into packets, each packet is supplied with an identification mark and is copied onto the media. The data of a certain stream are not contiguously positioned on the media, but are interrupted by packets of other streams. The identification marker of the packets enables SMS to restore the initial stream during reading.
Furthermore, SMS is able to split savesets across several media ( EOM = EndOfMedia ).
Supported encryption algorithms are the Advanced Encryption Standard (AES) 256-bit encryption and the Blowfish encryption. You can select the type of backup encryption under the Encryption and compression tab of the backup task properties. For every encryption you must create and store an encryption key. Data can be encrypted and compressed at the same time only if it is stored on tape, thus using the manufacturer's compression algorithms. If the data is stored to disk, it can either be encrypted or compressed, but not both.
The password cannot be longer than 28 characters and may not use any special characters (underscore, hyphen, etc.) Spaces are also not permitted.
Storing the encryption key during encryption
When a backup encryption is selected the encryption key is also encrypted in the Sesam database. This occurs and is backed up in the Task Table as well as being stored in - Table Results.
In the event the encryption key is changed the following tasks are undertaken with the new key and the new key is stored with the resulting backup. A restore of required data takes place with the use of the relevant key and the key is stored accordingly. A restore requires the entry of the key word.