[Gllug] AMD 64 X 2 / CentOS 4.3 x86-64 SMP RAID 5 slow

[Garry Heaton]

I've built a desktop server using:

Tyan Tomcat K8E / S2886
AMD 64 X2 4200+
LSI MegaRAID SATA 150-4
3 x WD Raptors 150GB,  10,000rpm
4GB RAM (max)

CentOS 4.3 x86-64 SMP
Boot option: iommu=soft (to take care of max 4Gb memory issues)
RAID 5

I set up the RAID5 array no problem within the MegaRAID bios. When loading
CentOS the only curiosity was that it loaded both the sata_nv and mbox
drivers. There were various long wait/hiccups during the first boot but the
sytem came up. I ran it at runlevel 5 and was shocked to find how slow the
desktop loaded and how slow menus opened. At first, that is. There seems to
be a pattern of apps and menus opening slowly first time after logging in
then as normal if reopened.

Basically the system, despite its impressive hardware, performs well below
my relatively meagre desktop (Athlon XP 2800 / 1GB RAM / 7200rpm disk / no
RAID). Is this something to do with RAID 5? The server will operate in
runlevel 3 when operational but I'd like to have confidence in the machine
seeing it zip along in both runlevels.

dmesg reported "many lost ticks" which could be a clue to maybe some AMD 64
X2 issues with SMP kernels.

Maybe I'd be better off running it with the single processor kernel instead?
Is 32-bit mode a waste of dual core CPU?

Garry
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