raid array seek performance

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

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.