Browse Prior Art Database

High-Speed Formatting Operation for a Disk File

IP.com Disclosure Number: IPCOM000105685D
Original Publication Date: 1993-Aug-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 101K

Publishing Venue

IBM

Related People

Francis, MH: AUTHOR

Abstract

Propsed is a formatting enhancement for disk files with small data buffers operating with fixed block architecture. It is simpler and quicker than conventional methods by using existing reallocation code so avoiding the difficulty of merging two defect lists in limited buffer space.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 51% of the total text.

High-Speed Formatting Operation for a Disk File

      Propsed is a formatting enhancement for disk files with small
data buffers operating with fixed block architecture.  It is simpler
and quicker than conventional methods by using existing reallocation
code so avoiding the difficulty of merging two defect lists in
limited buffer space.

      Disk files employing fixed block architecture have a large
number of data sectors, each comprising an ID field and a data field.
The ID field includes a unique address for each sector so that the
file's control system may quickly and reliably access the data in any
individual sector.  Before using ID fields must be initialized by the
file control system.  This process ('formatting') is carried out at
the time the file is manufactured but is also available as a command
which may be issued to the file by a device driver at any subsequent
time.

      The surfaces of all disks are imperfect, containing regions
which cannot be reliably read after being written.  The manufacturing
process for the file includes a step which identifies these areas
('defects') and lists them on the file itself.  In formatting
operations, the file control system reads this defect list and avoids
these defects when writing the ID and data fields.  Any sector which
would have included a defect is skipped over in its entirety.  Note
that this primary defect list is sorted into the order in which the
defects will be encountered during a subsequent formatting operation.
In addition, the file may have a grown defect list which is a list of
disk locations which were not detected as being defective at
manufacturing time but have subsequently been found.  Since these
defects are discovered at arbitrary, unscheduled times while the file
is in use, this list is not generally sorted.

      The sequence currently used for formatting is as follows.  The
primary defect list is read into the buffer and the grown defect list
is read into the same buffer.  Both defect lists are sorted together
into the order in which they will be encountered during the disk
formatting operation itself.  For each track, as it is about to be
formatted, the ID fields are built in the buffer, skipping any
sectors which are in the sorted defect list.  The IDs are written to
the track, skipping any defective sectors.  This procedure continues
until all the disk surfaces have been formatted over their entire
usable areas.

      A current trend in disk file technology is to have physically
smaller disk enclosures and associated control system leading to a
reduction in the amount of buffering on file.  A second trend is to
increase bit density on the disk surface.  Consequently, each bit has
a smaller area of medium associated with it so a small surface defect
which would previously have been too small to render a sector
unusable may now do so resulting in larger defect lists.  This
combination of reduced buffer size and increased de...