SCSI Description
5-14 Maxtor Atlas 10K III
The FORM AT UNIT command formats the disk's storage media into initiator-
addressable logical blocks according to initiator-defined options. This command
ensures that the disk storage media is format ted so that all data sector s are accessible.
Any data residing on the disk before this command is invoked is lost.
This command repairs damage left by previous WRITE LONG com mands. The
WRITE LONG command allows the i nitiator to deliberately corrupt a sector's ECC
or EDC.
Th e FORM A T UN IT comma n d u p d a te s th e d e fe c ti v e s e cto r list, ref e rre d to a s th e
Grown Defect List, that is maintained by the drive. As described below, the drive gives
the initiator considerable control over this list. If certification is enabled, all initiator-
addressabl e logic al blocks are verified, and bad sectors are reass igned and added to the
Grown Defect List.
During FOR M AT UNIT com mand processing, the dr ive ig-
nores th e Re ad/ Wr it e A WRE and AR RE b i ts ( fr o m Er ror Re -
covery Mode page) and does auto-revectoring as needed.
The drive is physically formatted when it leaves the manufacturing facility. Therefore,
it is n ot necess ary to r ef ormat the drive before using it. I f the log ical s ector siz e of t he
drive is cha nge d using t he Bloc k Desc r ipto r of the MODE SELECT Command, it is
recommended (but not necessary) to reformat the drive.
The Immed bit that can be included in the FORMAT UNIT command parameter
list allows the initia tor to control whether the drive returns completion status either
after fetching and validating the Command Descriptor Block and parameter list or
after the F ORM AT UNIT command completes. The FORMAT UNIT command
parameters are described in Table 5-11 and Table 5-12
Th e ti m e re q u i re d fo r the FORM A T U N IT com m an d to format the disk p r im ari ly
depends on the capacity of the drive. The number of defects detected and the number
of defects already in the Primary and Grown Defect Lists also influence the time
required to format the drive. If the Disable Certification bit is set to 1, formatting time
is reduced.
Defective sectors on the drive are managed through two lists: the Primary Defect Li st
and the Grown Defect List. The Primary Defect List is created when the drive is
man ufactured and is the drive's initial defect list. The Primary Defect List is not
affected by the FORMAT UNIT command. Sectors listed in it are revectored by the
drive. The Grown Defect List contains a list of the sectors that ha ve gone bad since
the drive's primary list was generated.
Def ects are communi ca ted in a data structu re referred to as a Defect De scriptor. The
SCSI specific ation defines several Defect Descriptor formats. The FORMAT UNIT
command recognizes defect descriptors in Block format, Bytes From Index format,
and Physical Sector format. (There is one exception: a value of FFFFFFFFh in either
the defect Bytes From Index field or the Defectiv e Sector Number fields is ignored).