This drive cannot sustain high speed writes. When swapped in as a replacement to increase capacity, we were surprised how slowly a standard Time Machine backup progressed, and investigated with some large-file write benchmarking.
Even when connected to a dedicated USB3.1 bus, my basic tests to the unit I bought, of a linear large-file write, showed that it can barely take 40MB/sec for a few seconds at the start of continuous writes, and then quickly degrades to 9MB/sec or worse; sometimes it stalls completely and write performance drops to nil.
By comparison, I have several comparable 5TB portable-backup drives from other manufacturers, and even other similar drives from WD, and these consistently sustain writes of 100MB/sec, using the same port and cable and test method.
It's possible that WD used a very low-quality platter and attempted to improve short-term performance with a buffer. That's a reliability as well as a performance problem. My assessment is that in any case, this drive is unsuitable for any long-running write, and is in particular, bad for backups.
Specific model to avoid is WDBPKJ0050 and this appears in your USB device tree as "WD My Passport 2627".
| Hard Drive | 5 TB |
|---|---|
| Number of USB 3.0 Ports | 1 |
