The Backup 3.4
From SEPsesam
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The Backup
Automatic Backups are monitored and initiated by the SEPuler. Data specified in task for backup are copied to saveset on the pre-selected media.
To speed up and simplify the restore of desired data 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
A full backup copies all source files precisely as they are. During a restore this version of the files is easily copied back from the media. Note: However, in some cases it represents a large amount of data. And may require an extended period to restore all files.
A differential backup copies only those files that have been changed or altered after the latest full backup. Since a smaller amount of files must be transferred, the backup time is shorter. In order to restore the whole data source, one must first copy back the files from the full backup before copying those of the differential one. This is a two-step process which is automatically scheduled and started by the Generation Restore mode of Sesam.
The incremental backup copies files changed since the previous backup regardless of type. This generates the smallest amount of data on the backup media. To restore the whole data source it is necessary to first copy back the saveset of the last full backup, and then all intermediate savesets. Therefore, depending on the administrator's backup strategy, the restore can contain several steps.
A copy backup is a full backup, however, without a change to the archive bits. A copy backup does not alter diff/incr backups of external backup systems.
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 snapshots is restricted to oper systems:
- under XP only one set (with some volumes) is allowed,
- other oper systems allow up to 64 sets.
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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 since the saveset has stored original paths.
See:
- "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.
System Requirements
- Client operating system: Windows XP, 2003, 2008
- Sesam Server from version 3.4.1.64
- Sesam Client from version 3.4.1.64
Activation of the VSS Shadow Backup
Establish a new backup task or modify an existing one for the client. Add option -o vss in field Save options in the task properties under tab Options 1. The task source is unchanged.
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For a system_state backup the option -o vss is already set, and should not be added again under Options 1! |
Parallel Backups
Sesam supports parallel i.e. simultaneous backup for several data sources onto one drive. This is denoted as 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 = End Of Media ).
Encryption
Starting with version 3.4 it is now possible to use AES 256 bit encryption in addition to the previously supported Blowfish encryption algorithm. You can select the type of encryption desired in "Option 2". You must create and store an encryption key for the data file to be encrypted.
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The password cannot be longer than 28 characters and may not use any special characters (underline, 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.
