9.1 Different types of data movement in IBM Spectrum Protect (TSM) Infrastructure

There are 2 main data movement types which are generally used for taking backup and archive from clients to TSM server.

Types of data Movement in TSM Infrastructure

Backup through Local Area Networks (LAN) & Wide Area Networks (WAN)
In a traditional LAN and WAN environment, the Tivoli Storage Manager  backup-archive client reads data from locally attached disks and sends it over  the LAN to the Tivoli Storage Manager server. The server receives the data, then writes it out to its storage pool — tape, disk, or optical media — based on predefined policies and server configuration. Data is read and written by both the Tivoli Storage Manager client and server machines. In  addition, control information is also sent over the LAN to the Tivoli Storage Manager server.

Restore operations also follow the same path in the opposite direction. Data is read by the Tivoli Storage Manager server, sent via the LAN to the client system, and  is written there on local attached storage devices.

Backup through Storage Area Networks (SAN)
SAN technology provides an alternative path for data movement between the Tivoli Storage Manager client and the server. Shared storage resources (disk, tape) are accessible to both the client and the server through the SAN. Data movement is off-loaded from the LAN and from the server processor and allows for greater scalability. LAN-free backups decrease the load on the LAN by introducing a Storage Agent. The Storage Agent can be thought of as a small Tivoli Storage Manager server (without a database or recovery log) that is installed and run on the Tivoli Storage Manager client. The Storage Agenthandles the communication with the Tivoli Storage Manager server over the LAN but sends the data directly to SAN attached tape devices, relieving the Tivoli Storage Manager server from the actual I/O transfer.
Backup through SAN in TSM
Image Source: IBM

From a technical point of view, a SAN topology also offers higher bandwidth and  therefore faster speed availability for data movement. In reality this depends heavily on attached storage device technology and the nature of the transferred data. Usually, large files such as databases are transferred faster via SAN than LAN. When transferring small files, SAN performance may radically decrease.Moreover, LAN-free backups do add some complexity to a Tivoli Storage Manager implementation. You need to be careful of how the SAN-attached backup storage devices are utilized — insufficient resource planning can create 
a storage device overload. 

Also Read: Storage Area Network (SAN) Basic Free Tutorials

Tape library sharing between multiple Tivoli Storage Manager servers also requires proper planning. Instead of only one Tivoli Storage Manager server and its LAN-free clients using the attached library, multiple servers and their clients are sharing the storage device. Storage area networks are beneficial when moving large files, such as database backups, and application data, such as Exchange, Domino, SQL, or Oracle. Local area networks are appropriate for file server backups of small files.

Backup and Restore Overview

A backup creates an additional copy of a data object to use for recovery. A data object might be a file, directory, or a user-defined data object, such as a database table. The backup version of this data object is stored separately in the Tivoli Storage Manager server storage repository. When you restore an object, you copy it back from the server to the client.

You can restore a file, a directory, or even a whole machine. You need to know two things:
  • Items to restore: file name, directory
  • The time in the past of the saved items, optional
By default, TSM always takes Progressive incremental backup if the backup type is not specified. This method is the standard backup method that the Tivoli Storage Manager backup- archive client uses. A full backup of new objects is followed by incremental backups. No additional full backups of are required after the first backup. There is no need to retransmit backup data that has not changed during successive backup operations. changed data unchanged data

Backup types available in TSM

Below are the commonly used backups using TSM. By using TDP, you can also archivelog backups of the database applications. By default, Tivoli Storage Manager uses the intelligent Progressive Incremental backup strategy. Only files that are changed or that are new are backed up, reducing the amount of data transfer on your network and system. With progressive backup, you do not need resource-intensive, full backups. Progressive backup provides faster restores because it needs to restore only the version of the file requested. Progressive backup backs up less data, thus saving network bandwidth, tapes, and management overhead. With UNIX symbolic links, only the path information that the symbolic link contains is backed up.
  • Incremental (complete)
  • Incremental by date
  • Incremental (without journal)
  • Journal-based
  • Always backups, selective or full
  • Logical volume backup
  • Image snapshot backup
  • Network Data Management Protocol (NDMP)
Incremental (complete) backup
The incremental backup function, also known as incremental (complete), backs up all the files that are changed since the last back up. Incremental backups also back up all of the files that are created since the last backup. The incremental backup function does not back up files that are excluded by the include-exclude list.

Incremental by date backup
A disk or volume is eligible for an incremental by date backup, if you have done at least one full incremental backup of that entire disk or volume. Running an incremental backup of only a directory branch or individual file does not make the disk or volume eligible for incremental by date backups.

To perform an incremental by date backup by using the GUI, select the Incremental (date only) option from the type of backup list menu, or use the incrbydate option with the incremental command. The following conditions apply to backup criteria:
  • The client backs up only those files with modification dates and times that are more recent than the date and time of the most recent incremental backup of the file system.
  • Files that the client adds after the most recent incremental backup are not backed up if their modification date and times are earlier than that backup date and times.
  • Files that are renamed after the most recent incremental backup, but otherwise remain unchanged, are not backed up.
Incremental backup by date does not check for frequency, new files, deleted files, changes in file attributes, or rebinding of files.

Also Read: Full vs Differential vs Incremental vs Progressive Incremental Backups 

Journal-based backup
Journal-based backups for Windows, UNIX, and Linux improve performance of incremental and selective backups by using the journal engine service to note the changed files, rather than using file scanning. When the journal engine service is installed and configured, journaling is used by default with incremental backups.

Incremental (without journal) backup
To run an incremental backup without using the journal database, select Incremental (without journal). The journal database is discussed later in the lesson.

Selective (always backup)
The selective backup always attempts to back up the objects that you select. Use a selective backup to back up specific files or directories, regardless of whether a current copy of those files exists on the server.

Image Snapshot Backups
Image backups are full volume backups for Windows clients, which use the snapshot function of Tivoli Storage Manager.

Logical volume backups
Logical volume backups improve the restore performance. Periodically, the logical volume is backed up, before the scheduled daily incremental backups. If a logical volume needs to be restored, the logical volume backup is restored first, followed by the subsequent incrementals.

Network attached storage (NAS)
Network attached storage (NAS) file system backups are enabled through the support of Network Data Management Protocol (NDMP). Tivoli Storage Manager Windows, AIX, and Solaris servers back up and restore network attached storage (NAS) file system images to automated tape drives or libraries. These libraries are attached to Network Appliance and EMC Celerra NAS file servers. NDMP support is available only on IBM Tivoli Storage Manager Extended Edition.

Journal-based backups

Journal-based backup provides an alternative to traditional progressive  incremental backup, which under certain circumstances may dramatically  increase overall backup performance. As the name already implies, journal-based backups have no effect on archive  processing. The main difference between journal-based backup and progressive  incremental backup is the method in which the list of backup candidate objects is derived.

A progressive incremental backup creates the list of files by scanning the entire file system on the client and comparing that list with a list of files on the server. For a journal-based backup, the Tivoli Storage Manager backup-archive client obtains the list of backups by examining the entries that the Journal Based Backup Daemon creates.
Journal-based backup is supported on UNIX, Linux, and all Windows clients except for clients that run on Windows Server 2003 for Itanium-based systems. If you install the journal engine service and it is running, by default, the incremental command automatically does a journal-based backup on selected file systems that the journal engine service monitors. Tivoli Storage Manager does not use the journaling facility that is inherent in Windows NTFS file systems or any other journaled file system. To perform a journal-based backup successfully, the following conditions must be met
  • You must set up the journal service to monitor the file system that contains the files and directories that are backed up.
  • Must run a full incremental backup successfully at least once on the file system that is backed up.
  • The file space image of the file system at the server must not be modified by an administrative command since the last full incremental backup.
  • The storage management policy for the files that are backed up must not be updated since the last full incremental backup.
Backup sets
A backup set is a group of active versions of files, copied onto portable media. Backup sets can be restored on the client locally, without the Tivoli Storage Manager server being available.

Although the creation of backup sets is not a client function, it is an important feature of backups. Using the most recent backup versions that the server stores, a Tivoli Storage Manager administrator can generate a complete set of client files (backup set). These backup sets are used to retain a copy of client files for a longer period of time (Instant Archive) or for recovery of a client system, without server or network, when the backup set is copied onto portable media and restored locally (Rapid Recovery).
  • The generate backupset command runs as a background process on the server.
  • The restore backupset command restores a backup set from the server, a local file, or a local tape device.

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