raid array seek performance

I'm just beginning the process of benchmarking and tuning a new server.
Something I really haven't done before. I'm using Greg's book as a guide.
I started with bonnie++ (1.96) and immediately got anomalous results (I
think).

Hardware is as follows:

2x quad core xeon 5504 2.0Ghz, 2x4MB cache
192GB DDR3 1066 RAM
24x600GB 15K rpm SAS drives
adaptec 52445 controller

The default config, being tested at the moment, has 2 volumes, one 100GB and
one 3.2TB, both are built from a stripe across all 24 disks, rather than
splitting some spindles out for one volume and another set for the other
volume. At the moment, I'm only testing against the single 3.2TB volume.

The smaller volume is partitioned into /boot (ext2 and tiny) and / (ext4 and
91GB). The larger volume is mounted as xfs with the following options
(cribbed from an email to the list earlier this week, I
think): logbufs=8,noatime,nodiratime,nobarrier,inode64,allocsize=16m

Bonnie++ delivered the expected huge throughput for sequential read and
write. It seems in line with other benchmarks I found online. However, we
are only seeing 180 seeks/sec, but seems quite low. I'm hoping someone
might be able to confirm that and. hopefully, make some suggestions for
tracking down the problem if there is one.

Results are as follows:

1.96,1.96,newbox,1,1315935572,379G,,1561,99,552277,46,363872,34,3005,90,981924,49,179.1,56,16,,,,,19107,69,+++++,+++,20006,69,19571,72,+++++,+++,20336,63,7111us,10666ms,14067ms,65528us,592ms,170ms,949us,107us,160us,383us,31us,130us

Version 1.96 ------Sequential Output------ --Sequential Input-
--Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
--Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec
%CP
newzonedb.z1.p 379G 1561 99 552277 46 363872 34 3005 90 981924 49
179.1 56
Latency 7111us 10666ms 14067ms 65528us 592ms
170ms
------Sequential Create------ --------Random
Create--------
-Create-- --Read--- -Delete-- -Create-- --Read---
-Delete--
files:max:min /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec
%CP
newbox 16 19107 69 +++++ +++ 20006 69 19571 72 +++++ +++ 20336
63
Latency 949us 107us 160us 383us 31us
130us

Also, my inclination is to default to the following volume layout:

2 disks in RAID 1 for system
4 disks in RAID 10 for WAL (xfs)
18 disks in RAID 10 for data (xfs)

Use case is minimal OLTP traffic, plus a fair amount of data warehouse style
traffic - low connection count, queries over sizeable fact tables (100s of
millions of rows) partitioned over time, insert-only data loading, via COPY,
plus some tables are populated via aggregation queries over other tables.
Basically, based on performance of our current hardware, I'm not concerned
about being able to handle the data-loading load, with the 4 drive raid 10
volume, so emphasis is on warehouse query speed. I'm not best pleased by
the 2 Ghz CPUs, in that context, but I wasn't given a choice on the
hardware.

Any comments on that proposal are welcome. I've got only a week to settle
on a config and ready the box for production, so the number of iterations I
can go through is limited.