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Speed testing a NAND external drive

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Recently purchased an intriguing external flash storage drive -- a Klevv R1 < https://amzn.to/3sRI9jq>. It advertises read/writes of 1000MB/s and comes with a split USB-A USB-C cable (which I like instead of remember to bring an adapter/hub).

Of course out of the box, I had to test it. BlackMagic measured it at 680/674...not at the advertised speed, but still pretty fast for a $70 hard drive.

But then after a few days of use, it had slowed down noticeably. Reformatted as HFS+ and tested, Reformatted as APFS and tested. Tested plugged into USB-C and then USB-A

What I'm noticing the first test BlackMagic runs, I get fairly high speeds ( but never the out of box speed), but if I let it loop, the speeds as it continues drops pretty, and recovers *somewhat*.

Here's a typically example of the write/read data points as it repeats the test.
627/602
618/583
528/582
58/588
101/589
56/593
104/594
50/584
20/599
385/597
46/598
105/605

As you can see, the read speed maintains, while the write speeds drop off a cliff.

What's going on here?
- is this just Blackmagic's tool testing method being "unfair" to this type of drive technology?
- is this the sign of a bad hard drive?
- is this just how 3D NAND flash drives behave?

Also to add, the speeds are connected direct USB-C. When I connect USB-A, I get a similar trend, just slower from the start.
198/363
54/365
30/366
98/364
61/360
160/361

Ideas? Opinions?

 

This topic was modified 2 months ago by appleseed

@appleseed looks like SSD does not have s very large reserve for Spares, so once you dirty full capacity of the drive, it is spending all its write time doing garbage collection.

Maybe. I have to wonder if BlackMagic Speedtest is really sending close to 500GB of data at it. When I did these tests, I had reformatted just prior.

@appleseed Reformatting the file system does not tell the SSD that the already written data is no longer useful. So as far as the SSD is concerned all those previously written data is still valid.

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