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If you set the RESOURCEUTILIZATION option to enable multiple client/server
sessions and are backing up direct to tape, you must also update the server
option MAXNUMP for client node maximum mount points allowed.
The following factors can affect the throughput of multiple sessions:
The server's ability to handle multiple client sessions. Is there sufficient
memory, multiple storage volumes, and CPU cycles to increase backup
throughput?
The client's ability to drive multiple sessions (sufficient CPU, memory, and so
on).
The configuration of the client storage subsystem. File systems that are
striped across multiple disks, using either software striping or RAID-5, can
better handle an increase in random read requests than a single drive file
system. A file system on a single drive may not see performance
improvement if it attempts to handle many random concurrent read requests.
Sufficient bandwidth in the network to support the increased traffic.
These are some potentially undesirable aspects of running multiple sessions:
The client could produce multiple accounting records.
The server may not start enough concurrent sessions. To avoid this, the
server MAXSESSIONS parameter must be reviewed and possibly changed.
A query node command may not summarize client activity.
15.4.2 Communication
This section covers client options to influence the performance and behavior of
communication protocols between client and server.
DISKBUFFSIZE
The DISKBUFFSIZE option specifies the maximum disk I/O buffer size (in
kilobytes) that the client may use when reading files. Optimal backup, archive, or
HSM migration client performance may be achieved if the value for this option is
equal to or smaller than the amount of file read ahead provided by the client file
system. A larger buffer will require more memory and may not improve
performance. This option replaces the formerly available
LARGECOMMBUFFERS option. We recommend keeping the default value
unless otherwise advised by IBM support.
TCPBUFFSIZE
The TCPBUFFSIZE option specifies the size of the internal TCP communication
buffer that is used to transfer data between the client node and the server. A
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IBM Tivoli Storage Manager Implementation Guide
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