What is TSM Storage Pool Hierarchy ?


To make the TSM Clients backup faster you should let the backup go in multiple streams or multiple sessions. However, multiple backup streams/sessions require more number of tape drives availability if the destination storage pool is a removable sequential media like tape. 

To address this problem, Tivoli Storage Manager (TSM) has the facility of sending multiple sessions data to a primary Diskpool initially and migrate it to primary tape storage-pool later when the tape drives are free. This method is called TSM Storage Hierarchy in terms of Tivoli Storage Manager. The storage pool hierarchy includes only primary storage pools, not copy storage pools or active-data pools.

Storage Pool Hierarchy in Tivoli Storage Manager

You can arrange storage pools in a storage hierarchies, which consist of at least one primary storage pool to which a client node backs up, archives, or migrates data. Typically, data is stored initially in a disk storage pool for fast client restores, and then moved to a tape-based storage pool, which is slower to access but which has greater capacity. The location of all data objects is automatically tracked within the server database.

Also Read: TSM Storage Pool Concepts (V7 Revised)

You can set up your devices so that the server automatically moves data from one device to another, or one media type to another. The selection can be based on characteristics such as file size or storage capacity. A typical implementation might have a disk storage pool with a subordinate tape storage pool. When a client backs up a file, the server might initially store the file on disk according to the policy for that file. Later, the server might move the file to tape when the disk becomes full. This action by the server is called Migration. You can also place a size limit on files that are stored on disk, so that large files are stored initially on tape instead of on disk.

For example, your fastest devices are disks, but you do not have enough space on these devices to store all data that needs to be backed up over the long term. You have tape drives, which are slower to access, but have much greater capacity. You define a hierarchy so that files are initially stored on the fast disk volumes in one storage pool. This provides clients with quick response to backup requests and some recall requests. As the disk storage pool becomes full, the server migrates, or moves, data to volumes in the tape storage pool. 

How to set-up Storage Pool Hierarchy in TSM

To establish a hierarchy, identify the next storage pool, sometimes called the subordinate storage pool. The server migrates data to the next storage pool if the original storage pool is full or unavailable. You can set up a storage pool hierarchy when you first define storage pools. You can also change the storage pool hierarchy later.

Also Read: TSM Administrator Daily routine tasks

You cannot establish a chain of storage pools that leads 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.

Example:

  • Define the storage pool named TAPEPOOL with tape deviceclass: 
 define stgpool TAPEPOOL tape  maxsize=nolimit maxscratch=100
  •  Define the storage pool named DISKPOOL with disk deviceclass
define stgpool DISKPOOL disk  maxsize=5M nextstgpool=TAPEPOOL highmig=85 lowmig=40
    
In the above example, the data will be migrated from DISKPOOL when the storagepool utilization reaches 85%.

Also Read: Restoring damaged Storagepool volumes

How to update an existing storagepool ?

To Update the storage-pool definition for BACKUPPOOL to specify that TAPEPOOL is the next storage pool defined in the storage hierarchy


 update stgpool BACKUPPOOL nextstgpool=TAPEPOOL




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