Typically, the default values for the client and server
options for TCP/IP work well.
Procedure
- If you set the TCPWINDOWSIZE option
to a value that is greater than 63 on either the Tivoli® Storage
Manager server or
client, you must enable TCP window scaling (as defined by RFC 1323)
in the TCP/IP settings. See the documentation for your operating system
for how to set the TCP receive window size.
- Typically the default values for the TCPWINDOWSIZE options
on the client and server are preferred. A larger window might improve
communication performance, especially on fast networks with high latency,
such as a long-distance wide area network (WAN) connection.
If
you decide to tune TCP/IP window sizes, review the following guidance.
- If you increase the size of the TCP/IP window, do so in increments.
For example, try doubling the value for the TCPWINDOWSIZE option
and observing the results before you increase the value again. A larger
value for the TCPWINDOWSIZE option does not always
give better performance.
Tip: Do not set the sliding window
size to be larger than the buffer space on the network adapter. The
window acts as a buffer on the network. A window size that is larger
than the buffer space on the network adapter might cause packets to
be lost on the network adapter. Because packets must be sent again
when they are lost, throughput might degrade.
- If the operating system automatically tunes the TCP receive
window size, consider setting the Tivoli Storage
Manager server TCPWINDOWSIZE option
to 0. Setting the option to 0 means
that server sessions use the receive window for the operating system.
If
the operating system cannot automatically tune TCP window size, do
not set TCPWINDOWSIZE option to 0.
- The window size that you set with the tcpwindowsize client
option might have to be a compromise for different operations on the
system. For example, you might have to use a value that is a compromise
between what works best for backup-archive client operations and what
works best for Tivoli Storage
Manager for Virtual Environments operations.
- For the TCPNODELAY option, use the
default value of YES. This setting disables
the Nagle algorithm and allows packets that are smaller than the MTU
size to be immediately sent.
- Windows systems
have a TCP auto-tuning feature that monitors session transfer statistics
and then adjusts the receive window as needed for optimal performance.
For Tivoli Storage
Manager servers
and clients that run on these systems, you might consider setting
the Tivoli Storage
Manager TCPWINDOWSIZE option
to 0 to use auto-tuning.
Tip: The TCP auto-tuning
feature is enabled by default on some versions of Windows, and disabled by default on others.
If you intend to use auto-tuning, ensure that it is enabled for the Windows system.
Always monitor operations after such changes to verify
that the performance is not degraded.