There are, of course, many answers to this question.  Many people have
noticed that HP's conservative choices in some configuration areas affect
performance, especially as compared to Solaris.  A couple examples:

  o 'fs_async' kernel parameter

      HP-UX by default makes all file systems I/O synchronous.  Sun[R],
      by contrast, defaults to asynchronous I/O and depends on the syncer.
      Changing this parameter's value from 0 to 1 can significantly
      increase write speeds, BUT at the risk of losing data in a system
      crash.  You can change this parameter using SAM.

  o 'async' NFS option

      Similar to local writes, NFS writes to a filesystem exported from an
      HP-UX system are synchronous by default.  Add the async option to
      your /etc/exports if you want to change that, but be sure to
      carefully read the exports(4) manpage first.

An abundance of performance tuning tips are provided by HP in the following
tuning guides:

  o HP-UX Workstation System Tuning and Performance Guide, 08/31/00:
    <http://www.hp-partners.com/tcl_public/html/technical_support/tuning.html>

  o HP-UX Kernel Tuning and Performance Guide v3.1, 03/15/00:
    <http://docs.hp.com/en/1219/tuningwp.html>