Faster Copying from One Drive to Another

It is unlikely to go faster reading from one, and writing to 2 drives, especially if it is the same source volume, as the 2 copies are unlikely to remain in sync, so you might be making 2 read requests to the source volume for different areas of the volume, one for each destination volume.

Also if you are sharing a single USB interface, you are going to be splitting the bandwidth among multiple drives.

If you are plugging each drive into a different USB-C port on the Mac, you might get full drive bandwidth for each drive.

If you are using a USB-C dock, then you will be sharing a single 10 gigabits/sec with all 3 drives.

If you are using a Thunderbolt dock, a lot depends on how the dock sets up each USB port, whether it is sharing a single USB chip, or if it has multiple and each USB port can have 10 gigabits/sec of its own. The Thunderbolt dock will have 40 gigabits to share, but if you are also driving a monitor or 2, some of that bandwidth it going to the monitor(s).

worx25 wrote:

Would it be possible to make a copy process from one drive to another faster if I was copying to two drives at once instead of 1?

Generally no. In fact it may make the transfer slower especially on macOS since macOS tends to "scan" & gather a list of items to copy from the source prior to the transfer. Sometimes when initiating a second copy request will pause the first one while processing the second request.

As others have mentioned, there are only so many system resources available & initiating more copies may cut into those resources. In fact, depending on the USB3 connection....having multiple transfers can greatly slow them down. Even Thunderbolt transfers can be slowed down since two Thunderbolt ports generally share the same controller so transfer rates are divided between them.

It is possible some third party apps may perform faster transfers than the Finder. Command line utilities may sometimes offer a bit more performance (they also tend to keep running in the background), but command line utilities require knowledge of the command line where there are absolutely no safety nets...even a simple typographical error can have catastrophic results.

When dealing with that much data, you need to be using very fast drives & cable connections....especially if you need to perform large transfers regularly. Otherwise, it takes the time it takes.

You’ll want to identify the storage hardware and connection involved, and the RAID levels in use.

Copying to RAID-5 is very slow, for instance.

RAID arrays built from HDDs are glacially slow, too.

For connections, USB 2.0 is really slow, while newer USB does better.

Copying member volumes in parallel is completely dependent on RAID level.

From, using RAID-1 and RAID-10, parallel copies, maybe.

To, using RAID-0, RAID-5, RAID-6, parallel copies, not so much.