Some of the disk bottlenecks for application server disks are:
a) Persistent store writes
b) Transaction logging (tlogs)
c) HTTP logging
d) Server logging

The disk I/O on an application server can be optimized using faster disks or RAID, disabling syschronous JMS writes, using JTA direct writes for tlogs, or increasing the HTTP log buffer.

The following steps provide you a roadmap to help tuning your application environment to optimize performance:
a) Understanding your performance objectives;
b) Measuring your performance metrics;
c) Locate your bottlenecks in your system;
d) Minimize the impact of the bottlenecks;
e) Achieve your performance goals.

More details can be found in the weblogic tuning guide. But I think the details about the general performance tuning in the docs in not very good. You can read the weblogic  related topics in it. After all, weblogic is their own. Their guide shall be the authoratative.