[gentoo-user] [OT] Curious hdparm results

[walt]

I have a usb3 docking station which is showing some behavior I don't
understand:

 #hdparm -t /dev/sdc

/dev/sdc:
 Timing buffered disk reads: 266 MB in  3.00 seconds =  88.59 MB/sec
 Timing buffered disk reads: 268 MB in  3.01 seconds =  89.05 MB/sec
 Timing buffered disk reads: 266 MB in  3.01 seconds =  88.43 MB/sec
 Timing buffered disk reads: 266 MB in  3.02 seconds =  88.10 MB/sec
 Timing buffered disk reads: 306 MB in  3.01 seconds = 101.72 MB/sec
 Timing buffered disk reads: 266 MB in  3.00 seconds =  88.59 MB/sec
 Timing buffered disk reads: 306 MB in  3.00 seconds = 101.84 MB/sec
 Timing buffered disk reads: 306 MB in  3.00 seconds = 101.86 MB/sec

That's all the same disk, repeating hdparm as fast as I could.  The
disk was not even mounted at the time, and no other disks were active.

Two very different but reproducible numbers, changing values at random
times.  The only thing I can think of is that the disk may be doing
a SMART self-test, but for some reason the USB connection prevents
me from accessing the data so I can't test my theory.

Any other ideas?