I never seen this fast of iso encoding before using shrink. It only happens when I encode from a SATA drive to a ATA133 one. 1.4 min. backup for a 4.7 gig. disk is not bad. Must be drive to drive transfer is much quicker than single drive.
What burner did you use?
I’d be impressed if you managed to get that data rate when encoding to MPEG-4
That’s quite logical: when using a single drive, the drive has to keep on switching between reading and writing on different places on the drive. In a dual drive setup, this issue doesn’t apply. It’s even better when the drives are on separate channels, controllers or even datalines :).
A very simple depiction of this.
1 drive: Drive_1_move_to_read_position -> Drive_1_read -> compute -> Drive_1_move_to_write_position -> Drive_1_write -> Drive_1_move_to_read_position etc…
2 drive: Drive_1_move_to_read_position -> Drive_1_read -> compute -> Drive_2_move_to_write_position -> Drive_2_write -> Drive_1_move_to_read_position etc…
I guess you get the picture