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3.3 Defect Management

C141-E163

3-11

3.3

Defect Management

3.3.1

Defect list

Information of the defect location on the disk is managed by the defect list. The following are defect
lists which the IDD manages.

•

P list (Primary defect list): This list consists of defect location information available at the disk
drive shipment and is recorded in a system space. The defects in this list are permanent, so the
INIT must execute the alternate block allocation using this list when initializing the disk.

•

D list (Data defect list):  This list consists of defect location information specified in a FORMAT
UNIT command by the INIT at the initialization of the disk.  This information is recorded in the
system  space  of  the  disk  drive  as  the  G  list.    To  execute  the  alternate  block  allocation,  the
FORMAT UNIT command must be specified.

•

G list (Growth defect list):  This list consists of defective logical data block location information
specified in a REASSIGN BLOCKS command by the INIT, information on defective logical data
blocks  assigned  alternate  blocks  by  means  of  IDD  automatic  alternate  block  allocation,
information specified as the D list, and information generated as the C list.  They are recorded in
the system space on the disk drive.

The INIT can read out the contents of the P and G lists by the READ DEFECT DATA command.

3.3.2

Alternate block allocation

The alternate data block is allocated to a defective data block (= sectors) in defective sector units by
means of the defect management method inside the IDD.

The INIT can access all logical data blocks in the user space, as long as there is no error.

Spare sectors to which alternate blocks are allocated can be provided in either "spare sectors in a
cell" or "alternate cylinders". See Subsection 3.1.2 for details.

The INIT can specify the size and area for spare sectors by the MODE SELECT command at the
time of the initialization of the disk.

Both of the following are applicable to the alternate block allocation.

•

Sector slip treatment: Defective sectors are skipped and the logical data block corresponding to
those sectors is allocated to the next physical sectors. This treatment is made on the same cell as
the defective sector's and is effective until all spare sectors in that cell are used up.

•

Alternate sector treatment: The logical data block corresponding to defective sectors is allocated
to unused spare sectors in the same cell or unused spare sectors in the alternate cylinder.

The  alternate  block  allocation  is  executed  by  the  FORMAT  UNIT  command,  the  REASSIGN
BLOCKS  command,  or  the  automatic  alternate  block  allocation.    Refer  to  OEM  Manual–Fibre
Channel  Specifications–for  details  of  specifications  on  these  commands.    The  logical  data  block  is
allocated to the next physically continued sectors after the above sector slip treatment is made.  On
the  other  hand,  the  logical  data  block  is  allocated  to  spare  sectors  which  are  not  physically
consecutive to the adjacent logical data blocks.  If a command which processes several logical data
blocks is specified, the IDD processes those blocks in ascending order of logical data block.