Play Ping-Pong for Faster File Flipping

Just a quick note: If you’re moving heavy data around, disk seeks can be a huge drain on performance. I was flipping Red One clips from .R3Ds into REDCODE-native .MOVs using FCP’s Log and Transfer function today. This operation is basically a file copy, with a bit of re-wrapping in the middle; it’s I/O-limited, not CPU- or GPU-limited.

• With the sources and destinations on the same SATA drive, I was seeing clips flip at the rate of about 17-19 Mbytes/sec.

• When I sent the flipped clips to a second SATA drive (of the same make, model, and degree of fullness), the flip rate went up to 33-38 Mbytes/sec, about twice as fast.

In the same-disk case, the heads had to seek back and forth between the .R3D being read and the .mov being written; in the two-disk case the source disk could simply move sequentially through the files being read while the destination disk wrote files one after the other. Not only was it faster, it was quieter—both disks emanated a purposeful hum and the occasional chuckle, rather than the frantic chattering of frenetic seeking.

So, if you’re flipping lots of clips, or doing other transformations that get bogged down by I/O, having sources and destinations on separate physical drives (not just two partitions on one drive!) can save you a lot of time.

Also, for you FCP fans: I have an article on FXScript over on the Apple Channel, part of my Wilt-sells-out series. Enjoy. (If you don’t use FCP, don’t bother; it won’t do you a lick of good.)