>I have an AIX client running very slow backups, we have been looking into a
>couple of things, when we noticed something strange. If we run an archive on
>the box instead of a selective backup the speed improves by like 4 times...

So many factors...apples, oranges, and grapefruit.  Various affecters, including
software level, may be involved.  In particular, keep the following in mind
(from my notes):

Selective Backup, more overhead than    Running a Selective Backup can be
 Archive                                expected to entail more overhead than a
                                        comparable Archive operation, in that
                                        more complex retention policies are
                                        involved in Backup policies than in
                                        Archive. Remember that Archive retention
                                        is based purely upon time, whereas
                                        Backup involves both time and versions
                                        decisions. File expiration candidates
                                        processing based upon versions (number
                                        of same file) is performed during client
                                        Backups (in contrast to time-based
                                        retention rules, which are processed
                                        during a later, separate Expiration).
                                        The more versions you keep, the more
                                        work the server is distracted with at
                                        Backup time.
  Richard Sims, BU