Installation and User's Guide

OverviewTwo types of data deduplication are available on Tivoli Storage Manager: client-sidedata deduplication and server-side data deduplication.Client-side data deduplication is a data deduplication technique that is used on thebackup-archive client to remove redundant data during backup and archiveprocessing before the data is transferred to the Tivoli Storage Manager sever. Usingclient-side data deduplication can reduce the amount of data that is sent over alocal area network.Server-side data deduplication is a data deduplication technique that is done by theserver. The Tivoli Storage Manager administrator can specify the datadeduplication location (client or server) to use with the DEDUP parameter on theREGISTER NODE or UPDATE NODE server command.EnhancementsWith client-side data deduplication, you can:v Exclude specific files on a client from data deduplication.v Enable a data deduplication cache that reduces network traffic between theclient and the server. The cache contains extents that were sent to the server inprevious incremental backup operations. Instead of querying the server for theexistence of an extent, the client queries its cache.Specify a size and location for a client cache. If an inconsistency between theserver and the local cache is detected, the local cache is removed andrepopulated.v Enable both client-side data deduplication and compression to reduce theamount of data that is stored by the server. Each extent is compressed beforebeing sent to the server. The trade-off is between storage savings and theprocessing power that is required to compress client data. In general, if youcompress and deduplicate data on the client system, you are usingapproximately twice as much processing power as data deduplication alone.The server can work with deduplicated, compressed data. In addition,backup-archive clients earlier than V6.2 can restore deduplicated, compresseddata.Client-side data deduplication uses the following process:v The client creates extents. Extents are parts of files that are compared with otherfile extents to identify duplicates.v The client and server work together to identify duplicate extents. The clientsends non-duplicate extents to the server.v Subsequent client data-deduplication operations create new extents. Some or allof those extents might match the extents that were created in previousdata-deduplication operations and sent to the server. Matching extents are notsent to the server again.BenefitsClient-side data deduplication provides several advantages:v It can reduce the amount of data that is sent over the local area network (LAN).v The processing power that is required to identify duplicate data is offloadedfrom the server to client nodes. Server-side data deduplication is always enabledChapter 2. Configure the Tivoli Storage Manager client 39