when reading or writing to a WHS box, you are only reading or writing from one drive at a time.
WHS uses what is basically spanning to create large drives out of many smaller drives.
unlike raid striping, this means that you are reading from one drive at a time, not multiple drives at one time.
if you look at the spanned image below, you will see that as drive 1 is filled (in the storage pool), the next files are written to drive 2, then when drive 2 is full it moves to drive 3, and so on.
RAID does not do this.
A striped RAID array of 4 drives would have all the same size blocks on each drive, and would read from all four drives at once.
depending on your block size (64kb, 128kb, etc), data is written to drive one in this block size, then drive 2, then drive 3, then drive 4, then back to drive 1, and so on.
this means that unless the file is smaller than the block size, you are reading parts of the file from multiple drives at the same time and thus can utilize the speed of all the drives in reading and writing.
this means that you are not normally limited by the speed of any one drive, as you can add all of the drives speeds together (not really but thats the simple explanation) to achieve higher reading and writing speeds.
this is an advantage of striping raid of spanning, pooling, or whatever you want to call it that WHS does.
you are never going to saturate a gige connection with a single ide drive, and it is doubtful you can actually do it on a single sata drive.
the interface to the drive may support it, but everything else in the computer is slowing it down.