SATA drives are designed to be faster and therefore have mechanical functions and specifications conducive to this end, hence they perform operations like formatting quicker. When a drive is reformatted through the "full Format" option (as opposed to the "quick" option) blocks of blank data (ie 1's & 0's) are written to the whole area of the drive completely erasing it (Quick formatting just erases the TOC or index so that the drive assumes its blank as it has no way to locate the data, which then gets progressivley overwritten in future use).
As regaurds stopping it half way through formatting, this would have no real implications if you are planning a full format anyway however it will screw up the function of the disk, ie you wont be able to use it until it is fully formatted, however it will not damage it no.
