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Chapter 3 System Preparation
HPSS Installation Guide September 2002 161
Release 4.5, Revision 2
Note that the ttcp tool is included in the deployment package and is not related to the Unix
ToolTalk service.
HPSS makes extensive use of a system’s networking capabilities. Therefore, the setting of the
tunable networking parameters for the systems on which the various HPSS servers and clients will
run can have a significant impact on overall system performance.
Under AIX, a utility is provided to display and modify a number of networking parameters. The
utility is _no_ (Network Options). Refer to the AIX Performance Tuning Guide, for details of each
option and its impact on networking and system performance.
Some options that typically impact performance within an HPSS system environment are:
AIX also provides a configuration attribute that controls the maximum amount of memory that can
be allocated to mbufs. It can be viewed or modified via smit (select “Process Environments”, then
“Change / Show Characteristics of Operating System”) or via the command line (“lsattr -E -l
sys0”, “chdev -e sys0 -a maxmbuf = <new value>”).
It is recommended that the available combination of options be tested as part of the initial HPSS
system testing. In particular, poor network performance has been experienced where options on
one system do not match options on other remote systems.
There are also attributes that are specific to the individual network interface that may affect
network performance. For example, the network interface for the IBM SP TB3 switch provides
Table 3-1 Network Options
Network Option Description
thewall Controls the maximum amount of system memory that
can be used by the system networking code. A value
that is too low can cause networking requests to be
delayed or denied. The recommendation from AIX
development is to set this value to at least two times the
maximum number of concurrent connections times the
size of the socket send/receive buffers. The default
setting for AIX 4.3.2 and later is the smaller of (1) half
the size of physical memory or (2) 1 GB.
sb_max Controls the maximum size allowed for send and
receive buffers for a socket.
udp_recvspace Controls the default size of the receive buffer for UPD/
IP sockets. A value that is too small can cause server
RPC sockets to be overrun.
tcp_recvspace, tcp_sendspace Controls the default size for the receive and send
buffers for TCP/IP sockets. Internally, HPSS servers
and clients attempt to set these buffers sizes explicitly,
but other utilities may not.
rfc1323 Controls whether large TCP window sizes are used.
Usually set to ON for higher throughput networks (e.g.,
HiPPI, SP switch) and set to OFF for lower throughput
networks (e.g., ethernet, FDDI).