Block size depending on usage:

• most typical workload on disks use 16k blocks for read and write
• on Spectrum protect, stgpool type DISK use 256k blocks for read and write
• on Spectrum protect, stgpool type Directory container use 180k blocks for read and 50kB for write

Typical ratio is 70% read and 30% write.

If you use 10 Gbit Ethernet adapters, enable flow control on the switch or router port that the AIX system is connected to. See your network administrator, or see the manuals for your router or switch to determine how to enable flow control.

If you set the TCPWINDOWSIZE option to greater than 63, set the rfc1323 network option to 1. To ensure that the new setting is used whenever the system is restarted, use the -p option on the command. For example, issue the following command:

no -o rfc1323=1 -p

If you see nonzero values for the no mbuf errors field in the output from the entstat commands, increase the value for the thewall option. Set the thewall option to at least 131072 and the sb_max option to at least 1310720. Newer versions of the AIX operating system have larger defaults for these options, and modifying them might not be necessary.

The TCPWINDOWSIZE option specifies, in kilobytes, the amount of receive data that can be buffered at one time on a TCP/IP connection. The sending host cannot send more data until it receives an acknowledgment and a TCP receive window update. Each TCP packet contains the advertised TCP receive window on the connection. A larger window lets the sender continue sending data, and may improve communication performance, especially on fast networks with high latency.

Note:

  To improve backup performance, increase the **TCPWINDOWSIZE** on the server. To improve restore performance, increase the TCPWINDOWSIZE on the client. The TCP window acts as a buffer on the network.
  A window size larger than the buffer space on the network adapter might degrade throughput due to resending packets that were lost on the adapter. The TCPWINDOWSIZE option is not related to the TCPBUFFSIZE option nor to the send and receive buffers allocated in client or server memory.

Specifies the size you want to use, in kilobytes, for the TCP/IP sliding window for your client node. You can specify a value from 0 to 2048. The default is 63. If you specify 0, the server uses the default window size set by the operating system. Values from 1 to 2048 indicate that the window size is in the range of 1 KB to 2 MB.