SM 17 B692/B694
B692/B694
Data
Overwrite
Security Unit
A copy or print job always starts writing data to disk, starting with the clusters at the
outer edge [A] and progressing toward the center.
The overwrite, on the other hand, always begins at the center cluster [B] and
progresses toward the edge.
Taking the first square as cluster 1 on the outermost track:
• A job starts writing from 1, 2, 3, and continues toward 32.
• At the end of the job , the Security module overwrite erase proceeds from the
opposite direction, starting from 32, 31, 30 on the innermost track and continues
to 1.
NOTE: Each number in the illustration represents 1 cluster, the smallest unit the
operating system uses to handle data on the HDD.
If a copy or print job starts during data overwrite, the job has priority and the
overwriting stops, and the copy or print job begins.
1
0
1
1
1
2
1
3
1
4
15
1
6
6
5
4
3
2
1
2
3
2
4
2
5
2
6
2
7
2
8
2
2
2
1
2
0
1
9
1
8
1
7
.
.
.
.
3
2
3
1
3
0
2
9
7
9
8
B692D902A.WMF
[A]
[B]
HDD Data
Overwrite