I am planning to buy a new PC that has a 12 TB hard drive for "random" data and files, no programs.

Now I also want a similar HDD to backup my files from time to time. The extrenal disk is usually at a completely different place than the PC, so from time to time I have to load everything that is on the big internal HDD to the external HDD. As you can imagine I need a fast connection if I don't want to sit forever. My current system is at about 4TB and needs nearly a whole day over USB 3.0 (top speed of 120MB/s for the newer disks, and about 80MB/s for older external HDDs).

Now my idea is to put the new Plate into an USB 3.1 Type-C enclosure.

Now here is my question: Are these kinds of hard disks fast enough, that USB 3.1 is an advantage, or would USB 3.0 allow fast enough transfer rates and it is simply the HDD that is the limit.


The ~120MB/s speed that you see is pretty standard for a hard disk, and indicates that the hard disk is the bottleneck - not the USB connection.

120MB/s comes to 960Mb/s (bytes vs bits), which is well within the theoretical 5Gb/s maximum of USB 3.0.

Writing a 4TB disk at this rate will indeed come to ~8.8 hours, and I would strongly advise against this approach for a 12TB disk.

As the backup is taking such a long time, I would suggest you look into a more suitable backup solution - perhaps one that only updates the backup disk with changes, rather than rewriting the entire disk each time.

If you're on Windows (assumption, apologies), then you might like to look into SyncToy.

If you're more comfortable with the command line, then I'd suggest looking into robocopy or rsync (wiki).

If you are running on a Linux / Mac / Unix-like system then rsync will likely already be available to you, but it can be run on Windows too. A simple "backup this stuff" invocation would look like this:

rsync -av "${SOURCE_DIR}" "${BACKUP_DIR}"

Depending on your data, these applications will likely save you a large amount time, and will also significantly reduce the stress put on your hard disks.

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  • 1
    Nice answer. And it combines also neatly with my answer. I didn't think he would be doing full-disk backups. I'm a sysadmin myself and rsync (or robocopy in Windows) is so natural to me I don't always realize that others may not be familiar with them. – Tonny Mar 1 '18 at 15:59
  • Thanks, and robocopy is what I was trying to think of! I might have to build that into my answer... – Attie Mar 1 '18 at 16:01
  • I guessed as much ;-) SyncToy is nice but is a lot slower than robocopy. – Tonny Mar 1 '18 at 16:06
  • Main reasoning is it's got the buttons... I also wonder about it's suitability as I'm sure it's been v2.1 for some years now. – Attie Mar 1 '18 at 16:08

Spinning platter harddisks are the limiting factor and have been so for several years now.
The only way around that is use a RAID solution: Multiple harddisk in parallel so the blocks of data that make up a file can be distributed across multiple disks that can be written to in parallel.

For a reasonably cheap solution in a home setting consider using a 2-disk NAS (with 2 disks of 6 TB) as backup medium. Some NAS boxes have (besides the normal LAN connection) also the ability to be used as a USB 3/3.1 and/or Thunderbolt external disk.
This would maximize your throughput with the read-speed of the internal harddrive being the most limiting factor.
You will have to read the fine-print in the manual very carefully. Many devices have the fast USB 3/3.1 or Thunderbolt interface but can not actually utilize the theoretical maximum speed due to limitations of their internal controller.

By the way: Using 1 Gb/s LAN to talk to a NAS gives an approx. 90 MB/s throughput under ideal circumstances. That is slightly slower tahn the read-speed of your internal harddisk so backup up via LAN is actually slower (unless you have 10 Gb/s LAN, but try to find an affordable NAS and network switch that can handle that).

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