Tivoli Storage Manager for Windows: Administrator's Guide


Overview of TSM Storage Area Network (SAN) Support

A storage area network (SAN) is a dedicated storage network that isolates access to shared data to improve system performance. A SAN differs from a typical network. A typical network not only provides data access, but also provides communications functions like electronic mail (e-mail), terminal connection, and application program communication. A SAN can allow you to consolidate storage, and can relieve the distance, scalability, and bandwidth limitations inherent in LAN and wide area network (WAN) environments.

Using a SAN with TSM allows the following functions:

TSM can use a SAN to enable the sharing of storage devices supported by the TSM device driver. This includes most SCSI devices, but does not include devices that use the GENERICTAPE device type. See Controlling All Devices With the TSM Device Driver for device driver setup information.

For information about supported Fibre Channel hardware and configurations, visit the TSM home page at the following address: http://www.tivoli.com/support/storage_mgr/tivolimain.html. Also see http://www.tivoli.com/support/storage_mgr/san/overview.html for detailed information on support.

How TSM Servers Share Devices Over a SAN

Figure 5 shows a SAN configuration in which two TSM servers share a library device.

Figure 5. Storage Area Network (SAN) Configuration. The servers communicate over the LAN. The library manager controls the library via the SAN. The library client stores data to the library devices via the SAN.

Storage Area Network (SAN) Configuration

When TSM servers share a storage device, one server, the library manager, controls device operations. These operations include mount, dismount, volume ownership, and library inventory. Other servers, library clients, use server-to-server communications to contact the library manager and request device service. Data moves over the SAN between each server and the storage device. See Configuring TSM Servers to Share SAN-Connected Devices.

TSM servers use the following features when sharing an automated library device:

Partitioning of the Volume Inventory
The inventory of media volumes in the shared library device is partitioned among servers. Either one TSM server owns a particular volume, or the volume is in the global scratch pool. No server owns the scratch pool at any given time.

Serialized Drive Access
Only one TSM server accesses each tape drive at a time. Drive access is serialized and controlled so that servers do not dismount other servers' volumes or write to drives where other servers mount their volumes.

Serialized Mount Access
The library device's autochanger performs a single mount or dismount operation at a time. A single server (library manager) performs all mount operations to provide this serialization.

How TSM Clients Directly Access Devices Over a SAN

Figure 6 shows a SAN configuration in which a TSM client directly accesses a library device to read or write data.

Figure 6. SAN Data Transfer. Client and server communicate over the LAN. The server controls the device on the SAN. Client data moves over the SAN to the device.

SAN Data Movement

SAN data movement by a client requires the installation of a storage agent on the client machine. The TSM server maintains the TSM database and recovery log and controls device operations. The storage agent on the client handles the data transfer to the device on the SAN. This implementation frees up bandwidth on the LAN that would otherwise be used for client data movement.

The following outlines a typical backup scenario for a TSM client that uses SAN data movement:

  1. The client begins a backup operation. The client and the server exchange policy information over the LAN to determine the destination of the backed up data.

    For a client using LAN-free data movement, the destination is a storage pool that uses a device on the SAN. That device must also be mapped for the client.

  2. Because the destination is on the SAN, the client contacts the storage agent, which will handle the data transfer. The storage agent sends a request for a volume mount to the server.
  3. The server contacts the storage device and mounts the appropriate media.
  4. The server notifies the client of the location of the mounted media.
  5. The client, via the storage agent, writes the backup data directly to the device over the SAN.
  6. The storage agent sends file attribute information to the TSM server and the server stores the information in its database.

See Configuring TSM Clients to Directly Access SAN-Attached Devices.

Note:
Support for SAN data movement is currently limited. See the TSM home page at http://www.tivoli.com/support/storage_mgr/tivolimain.html for the latest information on clients that support the feature.


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