Using the simultaneous-write function requires consideration
of factors such as storage devices and network configuration.
The following limitations apply:
- 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
- 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 accepted.
- You can back up or archive copies of files that were migrated
by a Tivoli® Storage
Manager for Space Management client
to the same Tivoli Storage
Manager server
to which they were migrated. However, the files are stored only in
the primary storage pool. As a best practice, create current backup
and archive versions of the files before the Tivoli Storage
Manager for Space Management client migrates
them.
- Target storage pools that are 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.
- Data deduplication has the following effects on simultaneous-write
operations:
- Simultaneous write during client store 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.
- Simultaneous write during server migration of data
- 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. 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.
- You cannot use the simultaneous-write function with Centera storage
devices.
- The COPYSTGPOOLS and ACTIVEDATAPOOLS parameters
are available only to primary storage pools that use NATIVE or NONBLOCK
data format. This parameter is not available for storage pools that
use the following data formats:
- NETAPPDUMP
- CELERRADUMP
- NDMPDUMP
- 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.