Quantum ProDrive 40S - Page 121

Appendix C Media Defect Handling and Error Correcting Code
ProDrive
40S
80S
Sectors/
Head
Head
track
CYL
0
1
2
CYL+I
0
1
2
NOTES:
CYL
0
x+O x+l
x+2
28
1 x+
xxxx
x+
35
2
3
4
140 141
5 x+ x+
x+
175 176
x
= logical block address
xxxx
= deallocated sector
30
37
142
177
Zone size is six tracks/zone (default)
x+
x+
x+
FIGURE C-2 Field Found Defects
25
26
27
x+ x+
32 33
34
53
54
55
x+ x+
67 68
69
165 166
29
x+ x+
207
208
36
Two software configuration "switches" (post Error and Automatic Reallocation) are available for host
control
of the field replacement operation. Post Error detennines whether or not the ProDrive will notify
the host every time corrected data is passed from the drive. Automatic Reallocation detennines whether
or
not, when corrected data is passed to the host, the drive will automatically add the physical location of that
sector onto the Replacement Sector Map, move that sector
of data into a replacement sector, then check that
the sector was properly duplicated. These two software switches allow the selection
of four possible
options by the host. The option desired by the host will be specified via the
SCSI Mode Select command.
(See Section 5.11.10.)
28
35
Option 1 (Post Error off, Automatic Reallocation om; This is a "no action" option. That is,
the host will not be infonned that corrected data is being passed, nor will the
ProDrive take any action to
map out the suspect sector.
Option 2 (Post Error off, Automatic Reallocation On)i This is a transparent replacement
option. When
corrected data is passed from the drive, it will not notify the host of the action. However,
the drive will automatically add the physical location
of the sector containing the corrected data onto the
Replacement
Sector Map, move that sector of data into a replacement sector, then verify that the move was
completed correctly.
Option 3 (Post Error on, Automatic Reallocation oft); Every time corrected data is passed to
the host, the
ProDrive will notify the host of the recovered error. The drive will not take action to map
out the suspect sector.
By logging suspect block addresses passed from the drive, the host can use the
SCSI REASSIGN BLOCKS
command or the FORMAT UNIT command to manage new defects. The REASSIGN BLOCKS command
Appendix C Media Defect Handling and Error Correcting Code C-3