Loosing some performance when distributing I/O

Question

I have distributed disk I/O operations
that I have one disk for datafiles and control
file, on the second disk there are redo logs
along with datafiles for undo tablespace,
on the third disk there are multiplexed redo logs
and control file. I have compared that configuration
by running some test select statements with
configuration where all files the database contains
are on the same disk and on the database with configuration of more disk the results were slower.
The both databases are the same (making one as
a physical copy of datafiles of second and recreating
control file), parameter files are the same.
Can the difference be due to not multiplexing redo logs
in database with single configuration? But there are
no redo logs used where just running select statement.
Can someone give me advise?
Thanks a lot,
P.

Answer 1

Like Syed Jaffar said, install statspack, and analyze stats reports.
And to help you, there is a metalink note
228913.1 : Systemwide Tuning using StatsPack Reports
I think that performances are no better to separate the data on several disks if there is only one controller card, in this case, the bottleneck are not the discs but the controller card.
Try statspack and report us the results.
Nicolas.