Quantum 10K II - Manual (Page 92)

SCSI Description
Quantum Atlas 10K II Ultra160/m SCSI Hard Disk Drives 5–25
5.10 FORMAT UNIT Command (04h)
The FORMAT 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 formatted so that all data sectors are
accessible. Any data residing on the disk before this command is invoked is lost.
This command repairs damage left by previous WRITE LONG commands. The
WRITE LONG command allows the initiator to deliberately corrupt a sector's ECC
or EDC.
The FORMAT UNIT command updates the defective sector list, referred to as the
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-addressable logical blocks are verified, and bad sectors are reassigned and
added to the Grown Defect List.
NOTE
During FORMAT UNIT command processing, the drive ignores the
Read/Write AWRE and ARRE bits (from Error Recovery Mode page) and
does auto-revectoring as needed.
The drive is physically formatted when it leaves the manufacturing facility.
Therefore, it is not necessary to reformat the drive before using it. If the logical
sector size of the drive is changed using the Block Descriptor 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 initiator to control whether the drive returns completion status either
after fetching and validating the Command Descriptor Block and parameter list or
after the FORMAT UNIT command completes.
The time required for the FORMAT UNIT command to format the disk primarily
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
List and the Grown Defect List. The Primary Defect List is created when the drive is
manufactured 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 have gone bad since
the drive's primary list was generated.
Defects are communicated in a data structure referred to as a Defect Descriptor. The
SCSI specification 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 Defective Sector Number fields is ignored).