I've done more testing using WS2008R2 and IDE Modes (AHCI/RAID/IDE), all using single volumes formatted as NTFS with 0% Fragmentation.
CONCLUSION
The short answer is, IDE is quickest, then RAID, and there is something wrong with AHCI (I assume a driver issue).
IDE MODE COMPARISON
I'm using the latest AMD Complete Chipset installation (March 2011)
Test: Single 7.7GB (8330383 bytes) MKV File transferred from WD20EARS to another WD20EARS then a SAMSUNG F3 1GB
IDE:
To WD20EARS , 81 Seconds = 100.5 MB/s
To SAMF3, 92 Seconds = 88.5 MB/s
RAID: (Just set to RAID in the bios, still single volumes)
To WD20EARS , 85 Seconds = 96 MB/s
To SAMF3, 95 Seconds = 85 MB/s
AHCI starts off OK, as the others,windows reports 120MB/s+, but about 1.5Gb in, it starts slowing down, by 50% of the file, it's below 50MB/s and by the end it's heading towards 40 MB/s..
WHS2011 quick look
Whilst I was at it, I installed WHS2011 and noticed a couple of things
Completely Fresh Install, 67 Processes, over 1Gb Cached Memory, I assume it's aimed at the "I want every feature possible out of the box" user, which is fine with 3GB of RAM it seemed to handle it all easily enough, the odd process did fire off while transferring files around which caused minor hiccups..
NETWORK LARGE FILE
And a quick best case network check,
From Microserver A (WS2008R2) WD20EARS, same 7.7Gb file, to Microserver B (WHS2011) 250Gb OS drive and a WD 1TB and timing the transfers for accuracy
Oddly, it's slightly quicker to the OS drive (The 250Gb one supplied by HP)..
WD 250GB = 87.8MB/s
WD 1TB = 84 MB/s
This intrigued me a little, either the older (And it's a green WD 1TB drive) is saturating at 84MB/s, or the SATA driver is also playing up a little, the OS drive is off the IDE controller (According to windows), the WD 1TB is off an AHCI SATA Channel..
eSATA
This never seemed to work, and I'd given up, but as soon as I set the IDE mode to RAID in the bios, it started working, and even thought I've swapped IDE modes now several times, it continues to work! Result..