Test disk speed on Ubuntu terminal

hdparm is a good place to start.

sudo hdparm -Tt /dev/sda

/dev/sda:
Timing cached reads:   12540 MB in  2.00 seconds = 6277.67 MB/sec
Timing buffered disk reads: 234 MB in  3.00 seconds =  77.98 MB/sec

sudo hdparm -v /dev/sda will give information as well.

dd will give you information on write speed. If the drive doesn't have a file system use of=/dev/sda. Otherwise, mount it on /tmp and write then delete the test output file.

sudo dd if=/dev/sdb1 of=/media/USBHDD1/output bs=80 k count=10k; rm -f /media/USBHDD1/output

10240+0 records in
10240+0 records out
83886080 bytes (84 MB) copied, 1.08009 s, 77.7 MB/s