What is the factor that affects file transfer speeds between HDDs?

What is the factor that affects file transfer speeds between HDDs?
The transfer speed is slower when I'm transferring a large file from one hard drive to another as compared to when I'm transferring the same file from the latter to the former.

i heard ide harddrives are faster on everything then SATA and etc

well...which hdd is faster?

Ravanx said:

What is the factor that affects file transfer speeds between HDDs?
The transfer speed is slower when I'm transferring a large file from one hard drive to another as compared to when I'm transferring the same file from the latter to the former.

Kirsch said:

I dont think you guys quite understand the OP's question

When the OP transfers a file from one HDD to another, its fast
When the OP transfers THE SAME FILE between the SAME HDDs (just the other way around), its slow

I believe it depends on the RECEIVING HDD's health (whether the HDD itself is fragmented, old, slow write speed, etc)

But what if both are equally fragmented:
The former hard drive is a WD Caviar Black.
The latter hard drive is a WD Caviar Green.
Black to Green slower than Green to Black.
Why is this so?

the limiting factor is write speed.. even an empty HDD can be read faster than it can be written to.