What's best—Copying video to 2 drives simultaneously—or one at a time?

"maybe I could just go ahead and drop both at one time to be copied."

Using Finder, how do you drop two camera files at one time to be copied to two separate destination drives?

Maybe you mean two consecutive drag/drop operations to two different destination drives, which will run concurrently.

If you have two different camera cards, you can do two separate Finder drag/drop operations to copy those concurrently to two different destination drives. There is nothing wrong with that. It will be faster.

OTOH if you have two files on a single camera card, the card I/O bandwidth will probably be maxed out on the first copy, so doing two won't make it much faster.

If you have a single destination drive and two camera cards, if the cards are SDXC V90 and if the destination drive is SSD, it is likely faster to concurrently copy the camera files to the single SSD. Reason: a typical Mac SSD or external SSD is 2x faster than a typical v90 SDXC card, so it can handle 2 incoming copies from the slower SDXC cards.

But if the destination is a mechanical drive, doing two concurrent copies to that destination will cause "seek contention" and can be slower than copying the two files sequentially.

Ian R. Brown wrote:

This is something I have often pondered.

Does it copy them consecutively or simultaneously?

If the latter, does that means the files will be more fragmented?

There is no reason for the files to be more fragmented, as they are being copied to separate drives.

The only question is the speed at which the source can serve the media. The OP mentioned a "camera", it is unclear if this is camera solid state storage, or a camera card. It could be that the card, or the USB connection, could be a bottleneck. In any case, the overall copy process should not take longer if done at once; but depending on the bottlenecks, it may not reduce the duration much, either.

The bottom line is, in principle, there is no reason why you can't have several copies proceeding at once; whether that is faster or not, it depends. If we were copying between fast SSD with fast connections, sure. With a slow camera card, doubtful.

If the 2 or more files are copying simultaneously where are they being copied to?

Is each one being copied to a separate place or are the files being intermixed?

If the drive was empty one file would be copied as a contiguous whole but if 2 or more were being copied simultaneously, what then . . . ?

Ian,

The OP was asking about copying the same file to two different drives. In this situation, since the destinations are different, the question of intermixing or fragmenting does not present itself.

We don't know, furthermore, if these are HD or SSD. If the latter, then fragmentation is somewhat of a moot point. There are no more "sectors" and seek time as in HD.

When on set or copying directly off camera cards I always use Hedge for Mac (now called Offshoot). You can designate multiple destinations for you files to copy to and the software will checksum the results for reliability. The copy process to multiple drives is done simultaneously.

On a slow camera card, it's simple reads, which it can handle doing for two files at once with no humanly noticeable speed difference.

Even HDDs are fast enough these days it doesn't really matter. Any slow down in copying two files will still be faster than waiting for the two files to copy one at a time.

Copying to two drives at once makes no difference. Drives are fast enough these days, it won't matter. The difference may be milliseconds that you won't perceive.

This is something I have often pondered.

Does it copy them consecutively or simultaneously?

If the latter, does that means the files will be more fragmented?