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motrek

macrumors 68030
Original poster
Sep 14, 2012
2,733
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Last week I started backing up some data to an external USB hard drive that I have (2.5", 5400 RPM, Western Digital, USB 2).

I formatted the drive as APFS, encrypted.

I'm backing up a folder with ~150 GB, in the form of ~100,000 files of varying sizes.

The first time I did this backup (really just a copy), it took about 40 minutes, which means an average of ~60 megabytes per second write speed, which is about what one would expect for writing many files (including small files) to a 2.5", 5400 RPM drive.

Now I'm doing the same thing a week later, nothing has changed, but instead of taking 40 minutes, it's on target to take about 8 hours (it's about half done).

Looking at Activity Monitor, the hard drive is writing at a rock-solid rate of 5-6 MB/s.

Anybody have any idea what might be going wrong here? That's many times slower than it should be, obviously, and the fact that it's at a constant rate suggests to me that it's being artificially capped by something but I have no idea what that something might be.

Ideas? Thanks in advance.
 
For an external platter-based hard drive (particularly a slow one), I'd suggest HFS+ instead of APFS.
 
For an external platter-based hard drive (particularly a slow one), I'd suggest HFS+ instead of APFS.

Eh. It worked well enough the first time I copied stuff to it. Just not this most recent time.
 
A) Are you using the exact same cables, hubs, interfaces, and wiring configuration as before?

B) Are you overwriting the previous files? Or is the new copy completely separate?

Question A is because a defective cable or other component could lower speeds to USB 2.x or USB 1.x speeds.

Question B is because APFS might be preserving the prior version of the file, which could add overhead to the copying process.
 
A) Are you using the exact same cables, hubs, interfaces, and wiring configuration as before?

Yes, all identical. Including which specific USB port I'm using on my Mini.

B) Are you overwriting the previous files? Or is the new copy completely separate?

Separate.
 
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