4.3 Tivoli Storage Manager Device Class Overview

A device class represents a set of storage devices with similar availability, performance, and storage characteristics. Tivoli Storage Manager manages these device types and also uses the device class to determine the device and storage volume type to use. Tivoli Storage Manager uses these device classes to do the following data actions
  • Storing backup, archive, or space-managed data, primary storage pools.
  • Storing copies of primary storage pool data, copy storage pools.
  • Storing database backups.
  • Exporting or importing Tivoli Storage Manager data.

Managing Tivoli Storage Manager Device Classes

Each device that is defined to Tivoli Storage Manager is associated with one device class. The device class specifies the device type and media management information, such as recording format, estimated capacity, and labeling prefixes

For random-access storage, Tivoli Storage Manager supports only the DISK device class. The DISK device class is predefined by Tivoli Storage Manager. However, you can define many storage pools that are associated with the DISK device class. You cannot modify the DISK device class.

Also Read: 6 types of device classes which are supported by IBM TSM

You can define additional device classes so that they reflect specific devices, media, and procedures. Use the following command to define additional device classes.
DEFine DEVClass DEVType=type of device

Based on the tape environment, an administrator with system privileges can define as many different device classes for tape storage pools as needed. Each tape device class is uniquely identified by its name. Not all device classes are available on all platforms. You can use tape device classes parameters to control the following information:
  • Whether you use cartridge or reel tape (DEVtype).
  • The maximum tapes that can be mounted simultaneously (MOUNTLimit)
  • The maximum minutes before an idle tape is dismounted (MOUNTRetention)
  • The tape volume naming convention (PREFIX)
  • The estimated volume capacity (ESTCAPacityy
  • The use of compression by the client or tape hardware does not increase capability.
The FILE device type lets you create sequential volumes by creating files on disk storage. To the server, these files have the characteristics of a tape volume. FILE volumes can also be useful when transferring data for purposes such as electronic vaulting or for taking advantage of relatively inexpensive disk storage devices. One device class might be associated with multiple storage pools. Each storage pool is associated with only one device class. Each device class is characterized by its device type, which indicates the type of storage volumes that are used to store data.

TSM Device Class
Image Source: IBM

Tivoli Storage Manager device drivers
The Tivoli Storage Manager device driver that Tivoli Storage Manager supports are

IBM device drivers: atape on AIX, IBMTape on Windows, Atdd on HP, which are required for some devices. If a device requires an IBM device driver, it is noted next to the device name. 

If the tape library is non-IBM, then you should use TSM SCSI device drivers instead of their own device drivers.

Supports third-party vendor device drivers if they are supplied by the hardware vendor and are associated with the GENERICTAPE device class.

Relation between Device class and storage pool

Each device is associated with a device class that specifies the device type and how the device manages the media. If you have two libraries, you need two device classes. Storage pools are mapped to a device class. Through this mapping, when data is written to, or accessed from, a storage pool, Tivoli Storage Manager is able to access it. If the device is not listed on the IBM support page, it is not supported.

Also Read: DISK vs FILE device classes performance

Watch below video to learn how to define FILE device class and storage pools

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