Second harddrive as slave on ata0 (UDMA100) or as master on ata1 (UDMA33)?

[Martin Sommerhein]

I am managing a remote machine where a second harddrive was added for me
by the hosting company.  I noticed that the second harddrive had been
added as slave on the first IDE controller (ata0).  As I assumed I would
get better performance by having it as master on the second controller
(ata1), I asked them to move the second drive over to the second master
controller (ata1).  So was done, but then I found that the same disk
showed up as UDMA33 compared to UDMA100 when added as a slave to the
first controller (ata0).


Some info:
-------------------------------------------------------------------
1. Second disk as slave on ata0:

# dmesg | grep ata
atapci0: <Intel ICH4 ATA100 controller> port 0xffa0-0xffaf,0-0x3,0-0x7,0-0x3,0-0x7 at device 31.1 on pci0
ata0: at 0x1f0 irq 14 on atapci0
ata1: at 0x170 irq 15 on atapci0
ad0: 76319MB <WDC WD800BB-00CAA1> [155061/16/63] at ata0-master UDMA100
ad1: 76319MB <WDC WD800BB-00DKA0> [155061/16/63] at ata0-slave UDMA100

2. Second disk as master on ata1:

# dmesg | grep ^ad
ad0: 76319MB <WDC WD800BB-00CAA1> [155061/16/63] at ata0-master UDMA100
ad2: 76319MB <WDC WD800BB-00DKA0> [155061/16/63] at ata1-master UDMA33
-------------------------------------------------------------------


So the question is, what will give me the best performance, having it on
the second master with UDMA33 or as a slave on the first controller as
UDMA100?

Best regards,
Martin

PS: Should this have been sent to freebsd-hardware at freebsd.org so please
tell me?