Points to remember when taking backup to multiple storagepools simultaneously


Tivoli Storage Manager (TSM) offers simultaneously writing data into multiple (primary, Copy & Activedata) storage pools at the same time. TSM Clients can transfer data to multiple storage pools if configured properly. Using the simultaneous-write function requires consideration of factors such as storage devices and network configuration.

You control the simultaneous-write function by specifying certain parameters when you define or update primary storage pools. You can control when data is written simultaneously. You can also specify the copy storage pools and active-data pools to which data is simultaneously written.

Specifying when the simultaneous-write operations occur You can specify simultaneous-write operations for any primary storage pool that is the target of client store sessions, server import processes, or server  Data-migration processes. 

Also Read: TSM Storage Pool Concepts (V7 Revised)

You can also disable the simultaneous-write function. To control the simultaneous-write function, use the AUTOCOPY parameter on the DEFINE STGPOOL or UPDATE STGPOOL commands for primary storage pools.

Limitations of using Simultaneous Write or Autocopy Operations

  • Data cannot be written simultaneously to copy storage pools and active-data pools during server data movements such as Reclamation, MOVE DATA processes, MOVE NODEDATA processes, Storage pool backup and Copy of active data to an active-data storage pool.
  • The only server-data movement process that can write data simultaneously is migration.
  • Simultaneous-write operations take precedence over LAN-free data movement. The operations go over the LAN, and the simultaneous-write configuration is honored.
  • Target storage pools used for simultaneous-write operations can have different device classes, if the device classes have compatible data formats. Performance is limited by the speed of the slowest device.
  • Limitations apply when a NAS backup operation is writing a TOC file. If the primary storage pool that is specified in the TOCDESTINATION in the copy group of the management class has copy storage pools or active-data pools defined, the copy storage pools and active-data pools are ignored. The data is stored only in the primary storage pool.

Data Deduplication has the following effects on simultaneous-write operations  

  • If client-side deduplication is enabled, it is disabled before simultaneous-write operations occur. Non-deduplicated data is simultaneously written to target storage pools.
Also Read: Difference between Server-side and Client-side Deduplication
  • If a primary storage pool is set up for server-side deduplication, all copy storage pools and active-data pools are removed from simultaneous-write operations. For example, suppose that your simultaneous-write configuration comprises a primary storage pool, a copy storage pool, and an active-data pool. And if the primary storage pool is set up for server-side deduplication, Data is written only to the primary storage pool.
  • If a primary storage pool is not set up for server-side deduplication, data is written simultaneously only to copy storage pools or active data pools that are not set up for server-side deduplication. For example, suppose that your simultaneous-write configuration comprises a primary storage pool, a copy storage pool, and an active-data pool. The primary storage pool and the active-data pool are not set up for server-side deduplication. However, the copy storage pool is set up for server-side deduplication. When simultaneous-write operations occur, data is written only to the primary storage pool and the active-data pool.

Controlling Simultaneous-Write OR Autocopy Operations

Specify a value for the AUTOCOPY parameter on the primary storage pool that is the target of data movement. (The default is to write data simultaneously during client store sessions and server import processes.) 

The AUTOCOPY parameter is not available for copy storage pools or active-data pools. IBM Tivoli Storage Manager provides the following options for controlling when simultaneous-write operations occur
  • To disable the simultaneous-write function, specify AUTOCOPY=NONE. This option is useful, if, for example, you have copy storage pools or active-data pools defined, and you want to temporarily disable the simultaneous-write function without having to delete and then redefine the pools.
  • To specify simultaneous-write operations only during client store sessions and server import processes, specify AUTOCOPY=CLIENT. During server import processes, data is simultaneously written only to copy storage pools. Data is not written to active-data pools during import processes.
  • To specify that simultaneous-write operations take place only during server data-migration processes, specify AUTOCOPY=MIGRATION. During server data migration, data is simultaneously written to copy storage pools and active-data pools only if the data does not exist in those pools. 
  • To specify that simultaneous-write operations take place during client store sessions, server data-migration processes, and server import processes, specify AUTOCOPY=ALL.
Also Read: Increase TSM server performance by following these guidelines
A primary storage pool can be the target for more than one type of data movement. For example, the next storage pool in a storage pool hierarchy can be the target for data migration from the primary storage pool at the top of the hierarchy. The next storage pool can also be the target for direct backup of certain types of client files (for example, image files). The AUTOCOPY=ALL setting on a primary storage pool ensures that data is written simultaneously during both server data-migration processes and client store sessions.




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