I have 4 external drives connected to my rpi4b (4G).  1 is a WD Blue SSD
connected to usb3 port with the rootfs.  The other 3 are HDDs connected through
an USB3 hub to the other rpi usb3 port.  One of the HDDs is much slower than
the other drives.  What 
are some diagnostice commands I could use to try to diagnose why the drive is
slower than the others?

Here are results of lsusb and hdparm outputs with my comments in { }.

pi@rpi4b:~ $ lsusb
Bus 002 Device 003: ID 059f:1065 LaCie, Ltd 
Bus 002 Device 004: ID 0bc2:ab28 Seagate RSS LLC 
Bus 002 Device 005: ID 152d:1561 JMicron Technology Corp. / JMicron USA
Technology Corp. JMS561U two ports SATA 6Gb/s bridge
Bus 002 Device 002: ID 2109:0815 VIA Labs, Inc. 
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 008: ID 05ac:921d Apple, Inc. 
Bus 001 Device 005: ID 05ac:911d Apple, Inc. 
Bus 001 Device 010: ID 05ac:020b Apple, Inc. Pro Keyboard [Mitsumi, A1048/US
layout]
Bus 001 Device 007: ID 03f0:134a HP, Inc Optical Mouse
Bus 001 Device 004: ID 05ac:1003 Apple, Inc. Hub in Pro Keyboard [Mitsumi,
A1048]
Bus 001 Device 006: ID 0080:a001  
Bus 001 Device 003: ID 2109:2815 VIA Labs, Inc. 
Bus 001 Device 002: ID 2109:3431 VIA Labs, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

pi@rpi4b:~ $ sync; sync; sudo hdparm -t /dev/sda
/dev/sda:  {4TB 2.5 HDD unknown rpm}
SG_IO: bad/missing sense data, sb[]:  70 00 05 00 00 00 00 0a 00 00 00 00 24 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 Timing buffered disk reads: 342 MB in  3.00 seconds = 114.00 MB/sec

pi@rpi4b:~ $ sync; sync; sudo hdparm -t /dev/sdc
/dev/sdc:  {8TB 3.5 HDD 5400rpm}
 Timing buffered disk reads: 100 MB in  3.01 seconds =  33.25 MB/sec

pi@rpi4b:~ $ sync; sync; sudo hdparm -t /dev/sdd
/dev/sdd:  {3TB 3.5 HDD 7200rpm}
 Timing buffered disk reads: 388 MB in  3.05 seconds = 127.37 MB/sec

pi@rpi4b:~ $ sync; sync; sudo hdparm -t /dev/sdb
/dev/sdb:  {WD Blue SSD 2.5 form factor, rootfs}
 Timing buffered disk reads: 576 MB in  3.00 seconds = 191.87 MB/sec

Why is /dev/sdc so slow runnning through same usb3 hub as /dev/sda and
/dev/sdd?  I don't think it is rotation speed of drives.

TIA/
  --Steven

--- SoupGate-Win32 v1.05