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Administrator's Guide


Selecting a Device Configuration

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:

Planning for Server Storage describes how to evaluate your current storage device environment. It also describes the requirements, advantages, and limitations of all these configurations to help you choose the best set up for your installation.

Local Area Network Configuration

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:

Manual
A collection of one or more drives that are loaded and unloaded by an operator.

SCSI
A SCSI-controlled automated library that includes one or more drives.

349X
An IBM 3494 automated library and associated drives.

External
A library that is controlled by a media management program rather than by Tivoli Storage Manager. This category includes StorageTek libraries controlled by Automated Cartridge System Library Software (ACSLS), and libraries that are controlled by Windows Removable Storage Manager (RSM).

For more detailed information, see Libraries.

Network-Attached Storage

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

Network- Attached Storage (NAS) Configuration

Tivoli Storage Manager tracks file system image backups on tape, but not individual files.

Tivoli Data Protection for NDMP and Other NAS Backup Methods

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.

Tivoli Data Protection for NDMP Backups

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:

Multiple Tivoli Storage Manager Servers Sharing Libraries

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.

Storage Area Network (SAN) Configuration

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:

Partitioning of the Volume Inventory
The inventory of media volumes in the shared library is partitioned among servers. Either one 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 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 autochanger performs a single mount or dismount operation at a time. A single server (library manager) performs all mount operations to provide this serialization.

LAN-Free Data Movement

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: 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:

  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.

  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, in the case of a tape library, mounts the appropriate media.
  4. The server notifies the client of the location of the mounted media.
  5. The client, through the storage agent, writes the backup data directly to the device over the SAN.
  6. The storage agent sends file attribute information to the server, and the server stores the information in its database.

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.

Note:
See the Tivoli Storage Manager home page at http://www.tivoli.com/support/storage_mgr/tivolimain.html for the latest information on clients that support the feature.

Server-Free Data Movement

Tivoli Storage Manager allows clients to directly back up and restore file system images between disk storage and tape devices accessible over a SAN. This server-free data movement is handled on behalf of the Tivoli Storage Manager server by an outboard data mover, such as the IBM SAN Data Gateway. The data mover must be able to execute the SCSI-3 extended copy command. Server-free data movers must have addressability to all the devices involved, which include disk and tape drives. The devices may be attached to the SAN through either direct Fibre-Attach or SCSI devices connected to a data mover.

Unlike traditional LAN and LAN-free backups and restores, data passes through neither the client nor the server. Instead, the data mover handles the data. In this way, backup and restore operations do not require resources from client or server processors or from the LAN. Because it will not be copying data, the Tivoli Storage Manager server can handle more concurrent client connections and server operations. In addition, the Tivoli Storage Manager client machine, not having to read and send data to the server, can handle a greater application load.

Figure 5 shows the movement of server-free data. The numbers (such as (1)) refer to numbers in the figure.

Figure 5. Server-Free Data Movement

Server-Free Data Movement

  1. The client initiates a backup or restore image request ((1)).
  2. The Tivoli Storage Manager server issues a mount request to the library ((2)).
  3. The data mover initiates a copy operation ((3)).
  4. The data is copied between the disk and the tape library ((4)).

Server-free operations transfer only volume images, not standard, file-level data. Images backed up by server-free data movement must be stored in storage pools with a data format of NONBLOCK. If the client cannot perform a server-free backup or restore, the operation fails over first to a LAN-free operation. If that operation cannot be performed, the client attempts a LAN-based backup or restore.

Server-free operations can restore LAN-based or LAN-free volume image backups. Table 4 describes the possible combinations.

Table 4. Data Format Support

Data Format LAN-Based Backup LAN-Free Backup Server-Free Backup LAN--Based Restore LAN-Free Restore Server-Free Restore
NATIVE Yes No Yes No
NONBLOCK Yes Yes Yes Yes

The Tivoli Storage Manager for Windows 2000 client can perform a server-free image backup of both raw volumes and volumes that contain the NTFS file system. Tivoli Storage Manager allows users to perform full-volume backups of online volumes. The volume image version matches the volume at the start of the backup. Depending on the value of the IMAGEGAPSIZE client option, either all or only the used blocks of an NTFS volume are backed up.

The Tivoli Storage Manager client allows server-free backup and restore of volume images between different volume layouts with the exception of software-based RAID-5 volumes and software-striped volumes. When restoring to a software-based mirror volume (RAID-1), Tivoli Storage Manager restores to the primary copy only and uses the operating system to resynchronize the stale mirrors. The client supports volume layouts such as striped and mirrored only on Windows 2000 dynamic disks.

Note:
These restrictions apply only to software-based RAID levels, and not to storage subsystems that come with hardware RAID controllers.

Tivoli Storage Manager monitors the SAN addresses of devices it knows about. If the address of a defined devices changes due to an event on the SAN, the new address will be discovered and updated.

Planning for Server Storage

This section discusses how to evaluate your environment to determine the device classes and storage pools for your server storage.

Most devices can be configured using the Device Configuration Wizard in the Tivoli Storage Manager Console. The Device Configuration Wizard is recommended for configuring devices. See Chapter 5, Configuring Storage Devices. The wizard can guide you through many of the following steps:

  1. Determine the storage devices that are available to the server. For example, determine how many tape drives you have that you will allow the server to use.

    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.

  2. Determine the device type and device class for each of the available devices. Group together similar devices and identify their device classes. For example, create separate categories for 4mm and 8mm devices.
    Note:
    For sequential access devices, you can categorize the type of removable media based on their capacity. For example, standard length cartridge tapes and longer length cartridge tapes require different device classes.
  3. Determine how the mounting of volumes is accomplished for the devices:
  4. If you are considering storing data for one Tivoli Storage Manager server using the storage of another Tivoli Storage Manager server, consider network bandwidth and network traffic. If your network resources constrain your environment, you may have problems using the SERVER device type efficiently.

    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.

  5. Determine the storage pools to set up, based on the devices you have and on user requirements. Gather users' requirements for data availability. Determine which data needs quick access and which does not.
  6. Be prepared to label removable media. You may want to create a new labeling convention for media so that you can distinguish them from media used for other purposes.


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