Epson 10020 - Manual (Page 191)

Error Detection and Correction Check
This test checks the ability of the hard disk drive to detect a
read/write error and to correct the data accordingly.
Note
This test destroys some data on the innermost cylinder of the
selected hard disk drive. This cylinder is reserved for
diagnostics, and is never used for storage by MS-DOS.
Therefore, data created by MS-DOS is not destroyed.
Select option 3 from the menu to start this test. You see these
messages:
The data on the highest physical cylinder
may be destroyed by this check.
Enter Y to start this check.
Enter N to return to the menu.
Press Y and then Enter to continue with the test. If no errors
occur, the program returns to the menu.
An error occurs only if the drive is malfunctioning. In this case,
back up all your files, and have the drive serviced immediately.
(The drive may be corrupting your data.)
Read, Verify Check
This test reads and verifies data from all tracks of the disk,
checking each cylinder and using both heads.
Select option 4 from the menu to start this test. The program
displays the number of each cylinder it finds. For example, with
a 20MB hard disk, the first message you see is:
Current cylinder is 614
The cylinder number counts down to 0.
D-34 Performing System Diagnostics