Quantum Q250 User Manual

HEAD 0
HEAD 1
•
•
•
HEAD 5
x
x
+ 32
x + 160
x + 1 x + 2
(Bad)
x + 34
XXXX
x +161
x + 162
x
= logical block address of initial sector
Q280: cylinder
x 190; Q250: cylinder x 126
(Assuming 512 byte logical block size)
XXXXX
= deallocated sector
x + 29 x + 30
x + 61
x + 62
x + 189
(spare)
Figure 4-5: Sparing of Field-Found Defective Sectors
x + 31
x + 63
x + 33
(spare)
Table 4-1 shows the number of sectors available for Models Q250 and
Q280.
Table 4-1:
Available
Spare and Defective Sectors
User Spare
Maximum
Defective
Model
Cylinders
Sectors
Sectors Sectors at Factory
Q250
823
103,698
1,646 50
Q280
823
156,370
1,646
80
4.2.3
creating the Defect Lists
Defect lists map the defective sectors. The lists are written on a
system reserved cylinder; the W-list is downloaded into buffer RAM
during power-on. Copies of the lists are replicated on every head of
the drive as backups. Before a read or write, the W-list is checked
to determine whether the sector is defective or not, and if so, the
location of the sector which replaces it. See the Sequence descrip-
tions, Figures 2-15 through 2-17.
Defect lists are created by the FORMAT UNIT command, the REASSIGN
BLOCKS command, or during read operations when Automatic Read
Reallocation is enabled.
4-8

Quantum Q250 Specifications

General

Brand	Quantum
Model	Q250
Category	Storage
Language	English