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In the conventional local area network (LAN) configuration, one or more tape or optical libraries are associated with a single Tivoli Storage Manager server. In a LAN configuration, client data, electronic mail, terminal connection, application program, and device control information must all be handled by the same network.
A storage area network (SAN) is a dedicated storage network that can improve system performance. On a SAN you can consolidate storage and relieve the distance, scalability, and bandwidth limitations of LANs and wide area networks (WANs). Using Tivoli Storage Manager in a SAN allows the following functions:
In a SAN you can share storage devices that are supported by the Tivoli Storage Manager device driver. This includes most SCSI devices, but does not include devices that use the GENERICTAPE device type. See Chapter 4, Attaching Devices to the Server System for device driver setup information.
For information about supported devices and Fibre Channel hardware and configurations, see the following Web sites:
The following sections describe ways that you can configure your storage devices to work with Tivoli Storage Manager:
In a local area network configuration, a drive or an automated library can be controlled by only one Tivoli Storage Manager server. Device control information and client backup and restore data flow across the LAN.
Tivoli Storage Manager supports the following categories of libraries:
For more detailed information, see Libraries.
Network-attached storage (NAS) file servers are dedicated storage machines whose operating systems are optimized for file-serving functions. NAS file servers typically do not run third-party software. Instead, they interact with programs like Tivoli Storage Manager through industry-standard network protocols, such as NDMP. Tivoli Storage Manager uses Tivoli Data Protection for NDMP to communicate with and provide backup and restore data for NAS file servers.
Tivoli Data Protection for NDMP backs up and restores images of complete file systems. NDMP allows the Tivoli Storage Manager server to control the backup of a NAS file server. The file server transfers the backup data to a drive in a SCSI-attached tape library. The NAS file server can be distant from the Tivoli Storage Manager server.
Figure 2. Network- Attached Storage (NAS) Configuration
Tivoli Storage Manager tracks file system image backups on tape, but not individual files.
Using Tivoli Data Protection for NDMP to protect NAS file servers allows
Tivoli Storage Manager to control operations while the NAS file server
transfers the data. To use a backup-archive client to back up a NAS
file server, mount the NAS file server file system on the client machine (with
either an NFS mount or a CIFS map) and back up as usual. The following
table compares the two methods:
Table 3. Comparing Tivoli Data Protection for NDMP and Tivoli Storage Manager Backup-Archive Client
Tivoli Data Protection for NDMP | Tivoli Storage Manager Backup-Archive Client |
---|---|
Network data traffic is less because the Tivoli Storage Manager server controls operations remotely, but the NAS file server moves the data locally. | Network data traffic is greater because all backup data goes across the LAN from the NAS file server to the client and then to the Tivoli Storage Manager server. |
Less file server processing is required to back up a file system because the backup does not use file access protocols such as NFS and CIFS. | More file server processing is required because file backups require additional overhead for file access protocols such as NFS and CIFS. |
The Tivoli Storage Manager server can be distant from the NAS file server and the tape library. | The Tivoli Storage Manager server must be within SCSI or Fibre Channel range of the tape library. |
When Tivoli Data Protection for NDMP backs up a NAS file server, it creates NAS file system image backups. The image backups are different from traditional Tivoli Storage Manager backups because the NAS file server transfers the data to the drives in the library. NAS file system image backups can be either full or differential image backups. The first backup of a file system on a NAS file server is always a full image backup. By default, subsequent backups are differential image backups containing only data that has changed in the file system since the last full image backup. If a full image backup does not already exist, a full image backup is performed.
If you restore a differential image, Tivoli Storage Manager automatically restores the full backup image first, followed by the differential image. Tivoli Storage Manager cannot restore individual files from full or differential image backups.
The following operations are not supported for data that has been backed up by using Tivoli Data Protection for NDMP:
Figure 3 shows a SAN configuration in which two Tivoli Storage Manager servers share a library.
Figure 3. Library Sharing in a Storage Area Network (SAN) Configuration. The servers communicate over the LAN. The library manager controls the library over the SAN. The library client stores data to the library devices over the SAN.
When Tivoli Storage Manager servers share a library, 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.
Tivoli Storage Manager servers use the following features when sharing an automated library:
Tivoli Storage Manager allows a client, through a storage agent, to directly back up and restore data to a tape library on a SAN. Figure 4 shows a SAN configuration in which a client directly accesses a tape, disk, or FILE library to read or write data.
Figure 4. LAN-Free Data Movement. Client and server communicate over the LAN. The server controls the device on the SAN. Client data moves over the SAN to the device.
LAN-free data movement requires the installation of a storage agent on the client machine. The server maintains the database and recovery log, and acts as the library manager to control 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 client that uses LAN-free data movement:
For a client using LAN-free data movement, the destination is a storage pool that uses a device on the SAN.
If a failure occurs on the SAN path, failover occurs. The client uses its LAN connection to the Tivoli Storage Manager server and moves the client data over the LAN.
This section discusses how to evaluate your environment to determine the device classes and storage pools for your server storage.
The servers can share devices in libraries that are attached through a SAN. If the devices are not on a SAN, the server expects to have exclusive use of the drives defined to it. If another application (including another Tivoli Storage Manager server) tries to use a drive while the server to which the drive is defined is running, some server functions may fail.
Also consider the storage resources available on the target server. Ensure that the target server has enough storage space and drives to handle the load from the source server.