IBM SG24-5131-00 manual AIX Parameter Settings, 4.1 I/O Pacing

•nv6000.database.obj 4.1.0.0

•nv6000.Features.obj 4.1.2.0

•nv6000.client.obj 4.1.0.0

and for HAView 4.3

•xlC.rte 3.1.4.0

•nv6000.base.obj 4.1.2.0

•nv6000.database.obj 4.1.2.0

•nv6000.Features.obj 4.1.2.0

•nv6000.client.obj 4.1.2.0

3.1.4AIX Parameter Settings

This section discusses several general tasks necessary to ensure that your HACMP for AIX cluster environment works as planned. Consider or check the following issues to ensure that AIX works as expected in an HACMP cluster.

•I/O pacing

•User and group IDs (see Chapter 2.7, “User ID Planning” on page 48)

•Network option settings

•/etc/hosts file and nameserver edits

•/.rhosts file edits

3.1.4.1 I/O Pacing

AIX users have occasionally seen poor interactive performance from some applications when another application on the system is doing heavy input/output. Under certain conditions, I/O can take several seconds to complete. While the heavy I/O is occurring, an interactive process can be severely affected if its I/O is blocked, or, if it needs resources held by a blocked process.

Under these conditions, the HACMP for AIX software may be unable to send keepalive packets from the affected node. The Cluster Managers on other cluster nodes interpret the lack of keepalives as node failure, and the I/O-bound node is “failed” by the other nodes. When the I/O finishes, the node resumes sending keepalives. Its packets, however, are now out of sync with the other nodes, which then kill the I/O-bound node with a RESET packet.

You can use I/O pacing to tune the system so that system resources are distributed more equitably during high disk I/O. You do this by setting high-

56 IBM Certification Study Guide AIX HACMP