"... In Theory, the write speed for a hard disk is approximately 150 MB/sec (for example. SATA). " ==> NO ... not even close. That's the interface speed --> the speed at which data can be transferred between the computer and the disk's buffer ... NOT the actual disk platters. The most important performance characteristics of a disk are the average seek time and the sustained transfer rate (which is largely a function of the rotational speed of a disk).
Also, the operation implied in your comment "... if an operating system is able to copy files from one location of the hard disk to another location of same disk ..." is the WORST operation you can do for performance. This results in a great deal of disk "thrasing" (the head moving back-and-forth) as it accesses data in two different locations. If you copy data from one disk to another disk (NOT just another partition on the same disk) you'll see MUCH better transfer speeds (but still nowhere near the interface rate).
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by: pcfreakerPosted on 2008-04-18 at 09:58:16ID: 21387583
Hi,
The actual speed depends on the Hard disk itself.
Observed speeds are normally slower since they include the time for the drive to physically seek to the location to be written to before the actual transfer from the drives cache to its physical platters can occur. If there is any other disk activity taking place the drives heads may need to reseek to the proper location on each transfer.
Some utilities measure in Mbps and Windows will on MegaBytes per second, meaning the total speed will be 1/8th of the Mbps reported.
I recommend enabiling the write cache as it speeds up data transfer:
http://www.ocmodshop.com/o
Brgds.