Tivoli Storage Manager for Windows: Administrator's Guide


Overview of How TSM Device Classes Represent Devices

Device classes are TSM storage objects that contain information about the device type and the media.

TSM supports many devices for storing data. Devices known to TSM may be devices that exist as real physical devices, such as a disk drive or a tape drive. Devices may also be logical devices, such as files on a disk (FILE device type) or storage on another server (SERVER device type).

At a minimum, each type of device requires a device class. The device class contains information for the management of devices and media that are of a specific device type. The device type determines whether TSM also requires a library and drive definition. For example, a manually mounted tape device requires a device class, a library, and a drive definition.

The Device Class for Random Access Devices

Disk devices access their media randomly and share a single, common TSM device class named DISK. Administrators cannot define other random access device classes. Do not define a TSM library for random access devices.

Disk Devices

Magnetic disk devices are the only devices in the random access category. All disk devices share the same TSM device type and device class: DISK. TSM has a predefined DISK device class.

Figure 121. Magnetic Disk Devices Are Represented by Only a Device Class

Magnetic Disk Devices Are Represented by Only a Device Class

Device Classes for Sequential Access Devices

Tape devices, other devices that use removable media, FILE device types, and SERVER device types are members of the sequential access category of devices. All of these devices access their data sequentially. A device class for a sequential device contains a device type and media management information.

For sequential devices, the device class also specifies a library. Figure 122 shows the contents of a device class for a typical sequential access device.

Figure 122. Contents of a Device Class for Sequential Access Devices

Contents of a Device Class for Sequential Access Devices

Sequential access device types begin to store data at the beginning of a volume, and append new data after existing data. As data is deleted or expired, the space is not immediately reused. The server can reclaim space later by using the reclamation process (see Reclaiming Space in Sequential Access Storage Pools for details).

Device Type

Every sequential access device class requires a TSM device type as part of its definition. A device type identifies a device as a member of a group of devices that share similar media characteristics, for example an 8MM device type for tape drives that use 8mm tape. Device types supported by TSM include the following:

FILE
This device type allows administrators to create sequential volumes by creating files on disk storage. To the TSM server, these files have the characteristics of a tape volume. The FILE device type does not require administrators to define library or drive objects; only a device class is required.

Administrators can use FILE volumes as a way to use disk storage without having to define volumes to TSM. FILE volumes can also be useful when transferring data for purposes such as electronic vaulting.

SERVER
This device type allows administrators to create volumes for one TSM server that exist as archived files in the storage hierarchy of another TSM server. These virtual volumes have the characteristics of sequential access volumes such as tape. Administrators must define a device class and a target server. No library or drive definition is required.

Virtual volumes can be used for:

See Using Virtual Volumes to Store Data on Another Server.

REMOVABLE MEDIA
TSM provides a set of specified removable media device types, such as 8MM for 8mm tape devices, or REMOVABLEFILE for Jaz or Zip drives. The GENERICTAPE device type is provided to support certain devices that do not use the TSM device driver. See Administrator's Reference for more information about supported removable media device types. Figure 123 shows that a removable media device such as a tape device is represented by a library and a drive in addition to a device class.

Figure 123. Removable Media Devices Are Represented by a Library, Drive, and Device Class

Removable Media Devices Are Represented by a Library, Drive, and Device Class

Library

For sequential access device types (excluding FILE and SERVER), administrators must specify a library in the device class definition. The library administrators specify must be one that was defined to TSM, as discussed in Libraries.

Media Management Information

Every sequential access device class contains media management information, such as recording format and labeling prefixes.

For more information about how TSM helps to manage media, see Chapter 6, Managing Removable Media Operations.


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