Why is transfer between two SATA HDDs so slow?

Question

I have plugged in my Macbook Pro's SATA hard drive into my PC, and downloaded MacDrive in order to access it.

I'm trying to copy about 100GB onto my PC's hard drive which is also SATA, the slowest SATA speed is 1.5Gb/s(192MB/s) right? I know in the real world advertised speeds are never reached.

The folder is currently copying at speeds of 1.6MB/s, and the fastest it's been is 5MB/s. Is the advertised speed really that over exaggerated or is something wrong. ~20 hours is just a little too long for my liking.

Basically I have no idea why it's so slow and how I can make it faster?

Is there some setting I need to change or some driver I need to install (I have just reinstalled Windows 7 and not put any drivers on it that may have come with the PC)

Answer 1

What is the RPM speed of the drives?

The first generation of of SATA has a maximum theoretical capacity of 1.5Gbps, but hard drives are much, much slower (SSDs not withstanding, those things are fast!), especially once you start taking into account that your macbookpro's harddrive is probably a slower (5400RPM as opposed to 7200RPM or 15000RPM), low-power drive. The SATA link speed is in no way an "advertised speed" other than to say "it is physically impossible for the data to transfer faster than this".

Copying data to your PC may also be slowed down by the fact that the PC drive might have to skip around and interrupt the copy to write other bits of information to the drive from other processes (no, not much you can do about this) if it's your system drive.

You also have to take into account that the source drive may not be perfectly defragmented, which will further slow down the data access speed as the drive has to move to different locations to fetch a particular file

It's not the SATA link that's bottlenecking, but the harddrives themselves (SATA is just a protocol for transferring data).

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All that being said, 1.6MB/s-5.0MB/s does sound a bit slow if both drives are connected to the same computer and you're copying data from one to the other. I would suspect that one of the drives is seeing a fair bit of data access from another process, but without benchmarking the individual drives you're using, it's hard to tell.