I have three different data "disk" drives on my system and I timed transferring 13 GB of data between. The drives are a standard 7500 RPM disk, a pair of 7500 RPM disks in RAID 0, and a solid state flash drive. The times in minutes and and seconds were as follows:
The first thing to notice is that if the source and destination drives are the same then times are much longer. The Flash drive was particularly bad.
The best time was from Flash to RAID 0, but in the reverse direction the time was poorer than a standard disk, suggesting that the flash has a fast read but a slow write.
Conclusion: for disk bound operations, such as transferring DV AVI files with little or no processing use different drives if practicable. In other words, set the scratch files drive to be other than the drive with the source files on it. If possible, put your source files on a flash drive and your scratch files on a RAID 0 drive.
Edit: Sorry for the poor table layout. Two or more consecutive spaces get converted into a single space for some reason.