IBM Tivoli Storage Manager for Windows Backup-Archive Clients ...

and before duplicate data can be removed. The default ensures that the server has
copies of whole files at all times, in either a primary storage pool or a copy storage
pool.
Important: For further data reduction, you can enable client-side data
deduplication and compression together. Each extent is compressed before it is sent
to the server. Compression saves space, but it increases the processing time on the
client workstation.
In a data deduplication-enabled storage pool (file pool) only one instance of a data
extent is retained. Other instances of the same data extent are replaced with a
pointer to the retained instance.
When client-side data deduplication is enabled, and the server has run out of
storage in the destination pool, but there is a next pool defined, the server will
stop the transaction. The Tivoli Storage Manager client retries the transaction
without client-side data deduplication. To recover, the Tivoli Storage Manager
administrator must add more scratch volumes to the original file pool, or retry the
operation with deduplication disabled.
For client-side data deduplication, the Tivoli Storage Manager server must be
Version 6.2 or higher.
Prerequisites
The following prerequisites apply to client-side data deduplication:
v When a client backs up or archives a file, the data is written to the primary
storage pool that is specified by the copy group of the management class that is
bound to the data. To deduplicate the client data, the primary storage pool must
be a sequential-access disk (FILE) storage pool that is enabled for data
deduplication.
v The value of the DEDUPLICATION option on the client must be set to YES. You
can set the DEDUPLICATION option in the client options file, in the preference
editor of the IBM Tivoli Storage Manager client GUI, or in the client option set
on the Tivoli Storage Manager server. Use the DEFINE CLIENTOPT command
to set the DEDUPLICATION option in a client option set. To prevent the client
from overriding the value in the client option set, specify FORCE=YES.
v Client-side data deduplication must be enabled on the server. To enable
client-side data deduplication, use the DEDUPLICATION parameter on the
REGISTER NODE or UPDATE NODE server command. Set the value of the
parameter to CLIENTORSERVER.
v Files on the client must not be excluded from client-side data deduplication. By
default, all files are included. You can optionally exclude specific files from data
deduplication.
v Files on the client must not be encrypted. Encrypted files and files from
encrypted file systems cannot be deduplicated.
v Files must be more than 2 KB. Files that are 2 KB or less are not deduplicated.
The server can limit the maximum transaction size for data deduplication by
setting the CLIENTDEDUPTXNLIMIT option on the server. See the Administrator's Guide
for details.
The following operations take precedence over client-side data deduplication:
v LAN-free data movement
42 IBM Tivoli Storage Manager for Windows Backup-Archive Clients: Installation and User's Guide