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Administrator's Guide


Overview: Storage Pools

A storage volume is the basic unit of storage, such as allocated space on a disk or a single tape cartridge. A storage pool is a collection of storage volumes. The server uses the storage volumes to store backed-up, archived, or space-managed files. The group of storage pools that you set up for the TSM server to use is called server storage. Storage pools can be arranged in a storage hierarchy.

The server has two types of storage pools that serve different purposes: primary storage pools and copy storage pools.

Primary Storage Pool

When a user tries to restore, retrieve, recall, or export file data, the requested file is obtained from a primary storage pool if possible. Primary storage pool volumes are always located onsite.

A primary storage pool can use random access storage (DISK device class) or sequential access storage (for example, tape or FILE device classes).

The server has three default, random access, primary storage pools:

ARCHIVEPOOL
In default STANDARD policy, the destination for files that are archived from client nodes

BACKUPPOOL
In default STANDARD policy, the destination for files that are backed up from client nodes

SPACEMGPOOL
For space-managed files that are migrated from Tivoli Space Manager client nodes (HSM clients)

The server does not require separate storage pools for archived, backed-up, or space-managed files. However, you may want to have a separate storage pool for space-managed files. Clients are likely to require fast access to their space-managed files. Therefore, you may want to have those files stored in a separate storage pool that uses your fastest disk storage.

Copy Storage Pool

When an administrator backs up a primary storage pool, the data is stored in a copy storage pool. See Backing Up Storage Pools for details.

A copy storage pool can use only sequential access storage (for example, a tape device class or FILE device class).

The copy storage pool provides a means of recovering from disasters or media failures. For example, when a client attempts to retrieve a file and the server detects an error in the file copy in the primary storage pool, the server marks the file as damaged. At the next attempt to access the file, the server obtains the file from a copy storage pool. For details, see Restoring Storage Pools, Using Copy Storage Pools to Improve Data Availability, Recovering a Lost or Damaged Storage Pool Volume, and Maintaining the Integrity of Files.

You can move copy storage pool volumes offsite and still have the server track the volumes. Moving copy storage pool volumes offsite provides a means of recovering from an onsite disaster.

An Example of Server Storage

Figure 10 shows one way to set up server storage. In this example, the storage defined for the server includes:

Policies defined in management classes direct the server to store files from clients in the ARCHIVE, BACKUP, or HSM disk storage pools. For each of the three disk storage pools, the tape primary storage pool is next in the hierarchy. As the disk storage pools fill, the server migrates files to tape to make room for new files. Large files may go directly to tape. For more information about setting up a storage hierarchy, see Overview: The Storage Pool Hierarchy.

You can back up all four of the primary storage pools to the one copy storage pool. For more information on backing up primary storage pools, see Backing Up Storage Pools.

Figure 10. Example of Server Storage

Example of Server Storage

To set up this server storage hierarchy, do the following:

  1. Define the three disk storage pools, or use the three default storage pools that are defined when you install the server. Add volumes to the disk storage pools if you have not already done so.

    See Configuring Random Access Volumes on Disk Devices.

  2. Define policies that direct the server to initially store files from clients in the disk storage pools. To do this, you define or change management classes and copy groups so that they point to the storage pools as destinations. Then activate the changed policy. See Changing Policy for details.
  3. Attach one or more tape devices, or a tape library, to your server system.

    To enable the server to use the device, you must enter a series of the following commands:

    DEFINE DEVCLASS

    DEFINE STGPOOL

    See Chapter 4, Using Tape Devices with Tivoli Storage Manager for more information. For detailed information on defining a storage pool, see Defining or Updating Primary Storage Pools.
  4. Update the disk storage pools so that they point to the tape storage pool as the next storage pool in the hierarchy. See Example: Updating Storage Pools.
  5. Define a copy storage pool. This storage pool can use the same tape device or a different tape device as the primary tape storage pool. See Defining a Copy Storage Pool
  6. Set up administrative schedules or a script to back up the disk storage pools and the tape storage pool to the copy storage pool. Send the volumes offsite for safekeeping. See Backing Up Storage Pools.

Defining or Updating Primary Storage Pools

This section provides a summary of parameters you can set and change for storage pools using the administrative command-line or the administrative Web interface. The section also provides examples of defining and updating storage pools.

Task Required Privilege Class
Define storage pools System
Update storage pools System or unrestricted storage

When you define a primary storage pool, be prepared to provide some or all of the information that is shown in Table 8. Most of the information is optional. Some information applies only to random access storage pools or only to sequential access storage pools. Required parameters are marked.

Table 8. Information for Defining a Storage Pool

Information Explanation Type of Storage Pool
Storage pool name

(Required)

The name of the storage pool. random, sequential
Device class

(Required)

The name of the device class assigned for the storage pool. random, sequential
Pool type The type of storage pool (primary or copy). The default is to define a primary storage pool. Once you define a storage pool, you cannot change whether it is a primary or a copy storage pool. random, sequential
Maximum number of scratch volumes

(Required for sequential access)

When you specify a value greater than zero, the server dynamically acquires scratch volumes when needed, up to this maximum number. sequential
Access mode Defines access to volumes in the storage pool for user operations (such as backup and restore) and system operations (such as reclamation and server migration). Possible values are:

Read/Write
User and system operations can read from or write to the volumes.

Read-Only
User operations can read from the volumes, but not write. Server processes can move files within the volumes in the storage pool. However, no new writes are permitted to volumes in the storage pool from volumes outside the storage pool.

Unavailable
User operations cannot get access to volumes in the storage pool. No new writes are permitted to volumes in the storage pool from other volumes outside the storage pool. However, system processes (like reclamation) are permitted to move files within the volumes in the storage pool.
random, sequential
Maximum file size To exclude large files from a storage pool, set a maximum file size. The maximum file size applies to the size of a physical file (a single client file or an aggregate of client files).

Do not set a maximum file size for the last storage pool in the hierarchy unless you want to exclude very large files from being stored in server storage.

random, sequential
Cyclic Redundancy Check (CRC) Specifies whether the server uses CRC to validate storage pool data during audit volume processing. For additional information see Data Validation During Audit Volume Processing.

Using the CRC option in conjunction with scheduling audit volume processing continually ensures the integrity of data stored in your storage hierarchy. If you always want your storage pool data validated, set you primary storage pool crcdata definition to YES.

random, sequential
Name of the next storage pool Specifies the name of the next storage pool in the storage pool hierarchy, where files can be migrated or stored. See Overview: The Storage Pool Hierarchy. When defining copy storage pools to primary pools that have defined next pools, the copy pool list for each primary pool should be the same. Defining different copy pool lists can cause resources to be freed when failing over to the next pool. If the resources are freed, it can delay the completion of client operations. random, sequential
Migration thresholds Specifies a percentage of storage pool occupancy at which the server begins migrating files to the next storage pool (high threshold) and the percentage when migration stops (low threshold). See Migration of Files in a Storage Pool Hierarchy. random, sequential
Migration processes Specifies the number of processes that are used for migrating files from this storage pool. See Migration for Disk Storage Pools. random
Migration delay Specifies whether migration of files should be delayed for a minimum number of days. See Keeping Files in a Storage Pool and How Tivoli Storage Manager Migrates Data from Sequential Access Storage Pools. random, sequential
Continue migration process Specifies whether migration of files should continue even if files do not meet the requirement for migration delay. This setting is used only when the storage pool cannot go below the low migration threshold without moving additional files. See Keeping Files in a Storage Pool and How Tivoli Storage Manager Migrates Data from Sequential Access Storage Pools. random, sequential
Cache Enables or disables cache. When cache is enabled, copies of files migrated by the server to the next storage pool are left on disk after the migration. In this way, a retrieval request can be satisfied quickly. See Using Cache on Disk Storage Pools. random
Collocation With collocation enabled, the server attempts to keep all files belonging to a client node or a client file space on a minimal number of sequential access storage volumes. See Keeping a Client's Files Together: Collocation. sequential
Reclamation threshold Specifies what percentage of reclaimable space can accumulate on a volume before the server initiates a space reclamation process for the volume. See Choosing a Reclamation Threshold. sequential
Reclamation storage pool Specifies the name of the storage pool to be used for storing data from volumes being reclaimed in this storage pool. Use for storage pools whose device class only has one drive or mount point. See Reclaiming Volumes in a Storage Pool with One Drive. sequential
Reuse delay period Specifies the number of days that must elapse after all of the files have been deleted from a volume, before the volume can be rewritten or returned to the scratch pool. See Delaying Reuse of Sequential Access Volumes. sequential
Copy Storage Pools Specifies the names of copy storage pools where copies of files being stored in the primary storage pool, during client backup, archive or HSM stores, are also simultaneously written to all listed copy storage pools. This option is restricted to only primary storage pools using NATIVE or NONBLOCK data format. See the Copy Continue entry and Simultaneous Write to a Primary Storage Pool and Copy Storage Pools for related information.

Notes:

  1. The COPYSTGPOOLS parameter is not intended to replace the BACKUP STGPOOL command. If you use the copy storage pools function, ensure that the copy of the storage pool is complete by using the BACKUP STGPOOL command.

  2. When defining copy storage pools to primary pools that have defined next pools, the copy pool list for each primary pool should be the same. Defining different copy pool lists can cause resources to be freed when failing over to the next pool. If the resources are freed, it can delay the completion of client operations.
sequential
Copy Continue Specifies how the server should react to a copy storage pool write failure for any of the copy storage pools listed in the COPYSTGPOOLS parameter. With a value of YES, during a write failure, the server will exclude the failing copy storage pool from any further writes while that specific client session is active. With a value of NO, during a write failure, the server will fail the entire transaction including the write to the primary storage pool. sequential

Example: Defining Storage Pools

For this example, suppose you have determined that an engineering department requires a separate storage hierarchy. You want the department's backed-up files to go to a disk storage pool. When that pool fills, you want the files to migrate to a tape storage pool. You want the pools to have the following characteristics:

You can define the storage pools in a storage pool hierarchy from the top down or from the bottom up. Defining the hierarchy from the bottom up requires fewer steps. To define the hierarchy from the bottom up, perform the following steps:

  1. Define the storage pool named BACKTAPE with the following command:
    define stgpool backtape tape
    description='tape storage pool for engineering backups'
    maxsize=nolimit collocate=yes maxscratch=100
    
  2. Define the storage pool named ENGBACK1 with the following command:
    define stgpool engback1 disk
    description='disk storage pool for engineering backups'
    maxsize=5m nextstgpool=backtape highmig=85 lowmig=40
    

Restrictions:

  1. You cannot establish a chain of storage pools that lead to an endless loop. For example, you cannot define StorageB as the next storage pool for StorageA, and then define StorageA as the next storage pool for StorageB.

  2. The storage pool hierarchy includes only primary storage pools, not copy storage pools.

Example: Updating Storage Pools

You can update storage pools to change the storage hierarchy and other characteristics.

For example, suppose you had already defined the ENGBACK1 disk storage pool according to the previous example. Now you have decided to increase the maximum size of a physical file that may be stored in the storage pool. Use the following command:

update stgpool engback1 maxsize=100m

Task Tips for Storage Pools

Table 9 gives tips on how to accomplish some tasks that are related to storage pools.

Table 9. Task Tips for Storage Pools

For this Goal Do This For More Information
Keep the data for a client on as few volumes as possible Enable collocation for the storage pool Keeping a Client's Files Together: Collocation
Reduce the number of volume mounts needed to back up multiple clients Disable collocation for the storage pool Keeping a Client's Files Together: Collocation
Perform a simultaneous write to a primary storage pool and copy storage pools Provide a list of copy storage pools when defining the primary storage pool. Simultaneous Write to a Primary Storage Pool and Copy Storage Pools
Specify how the server reuses tapes Set a reclamation threshold for the storage pool

Optional: Identify a reclamation storage pool

Reclaiming Space in Sequential Access Storage Pools
Move data from disk to tape automatically when needed Set a migration threshold for the storage pool

Identify the next storage pool

Migration for Disk Storage Pools
Move data from disk to tape automatically based on how frequently users access the data or how long the data has been in the storage pool Set a migration threshold for the storage pool

Identify the next storage pool

Set the migration delay period

Migration for Disk Storage Pools
Back up your storage pools Define a copy storage pool

Set up a backup schedule

Defining a Copy Storage Pool

Automating a Basic Administrative Command Schedule

Have clients back up directly to a tape storage pool Define a sequential access storage pool that uses a tape device class

Change the policy that the clients use, so that the backup copy group points to the tape storage pool as the destination.

Defining or Updating Primary Storage Pools

Changing Policy

Simultaneous Write to a Primary Storage Pool and Copy Storage Pools

To simultaneously write data to a primary storage pool and one or more copy storage pools, you can specify a list of copy storage pools in a primary storage pool definition using the COPYSTGPOOLS parameter. When a client backs up, archives, or migrates a file, the file is written to the primary storage pool and is simultaneously stored into each copy storage pool. If a write failure occurs for any of the copy storage pools, the COPYCONTINUE parameter setting determines how the server should react. See Table 8 for additional information about storage pool definitions.

When using copy storage pools for the simultaneous write of data to a primary storage pool and associated copy storage pools, be sure that all resources, such as enough drives, are available for the write operation. For example, each simultaneous write operation will need all of the volumes to be simultaneously mounted. This requires that the number of available drives must be equal to or greater than the number of volumes to be simultaneously mounted. For additional information, see Mount Limit and the REGISTER NODE command in the Administrator's Reference for information about the MAXNUMMP parameter.

Note:
When defining copy storage pools to primary pools that have defined next pools, the copy pool list for each primary pool should be the same. Defining different copy pool lists can cause resources to be freed when using the next pool. If the resources are freed, it can delay the completion of client operations.


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