Manipulating disk partitions between disks

Details Manipulating disk partitions between disks Manipulating disk partitions between disks

1997-07-24

2001-01-23

Cabeca, John W. (Department: 2751)

Electrical computers and digital processing systems: memory

Storage accessing and control

Control technique

C711S173000, C711S112000

Reexamination Certificate

active

06178487

ABSTRACT:

FIELD OF THE INVENTION
The present invention permits manipulation of selected partitions of a computer disk drive. More particularly, the present invention relates to a method for safely shrinking, expanding, moving, and copying hard disk partitions.
TECHNICAL BACKGROUND OF THE INVENTION
Computers utilize a wide variety of disks to store data. Disks are classified according to the storage medium employed, such as when “optical” disks are distinguished from “magnetic” disks. Disks are also classified as either “floppy” or “hard.” Hard disks generally have greater storage capacity, faster data access times, and longer useful lives than floppy disks (“floppies”). Unlike hard disks, however, floppies are “removable.” That is, floppies are easily released from, and reattached to, a disk drive which provides the computer with access to the data on the disk.
FIG. 1
illustrates a disk
10
attached to a disk drive
12
. The disk
10
illustrates physical characteristics of both floppies and hard disks. The disk
10
contains a number of concentric data cylinders such as the cylinder
14
. The cylinder
14
contains several data sectors, including sectors
16
and
18
. The sectors
16
and
18
are located on an upper side
20
of the disk
10
; additional sectors may be located on a lower side
22
of the disk
10
. The sides
20
,
22
of the disk
10
define a platter
24
. Floppy disks contain only one platter and thus are either single-sided or double-sided. For clarity of illustration only one platter
24
is shown in
FIG. 1
, but hard disks often contain several platters and thus may include one, two, or more sides.
The upper side
20
of the disk
10
is accessed by a head
26
mounted on an arm
28
secured to the drive
12
. To access different cylinders of the disk
10
, the arm
28
moves the head
26
in toward the center of the disk
10
or out toward the periphery of the disk
10
according to the position of the desired cylinder. To access different sectors within a cylinder, the drive
12
rotates the disk
10
around a spindle
30
, thereby rotating the desired sectors into adjacency with the head
26
. Additional sides of a disk, including sides on additional platters, may be accessed in a similar manner by additional disk drive heads. Because each side of a disk is accessed by a corresponding disk drive head, the number of heads is sometimes used to indicate the number of sides of the disk that are accessible to the drive. For example, double-sided disks are accessed with double-headed drives.
A given sector on the disk
10
may be identified by specifying a head, a cylinder, and a sector within the cylinder. Heads are generally numbered from the top of the drive proceeding downward, beginning at zero. Cylinders are generally numbered from the outside edge of the platter proceeding inward, beginning at zero. Sectors within a cylinder are generally numbered from a marker in the disk medium proceeding either clockwise or counter-clockwise, depending on the direction of disk rotation in the disk drive, and beginning at one. A triplet specifying the head number, cylinder number, and sector number in this manner is known as a “physical sector address.” For instance, the sector labeled as
16
in
FIG. 1
could have a physical sector address of (head zero, cylinder seven, sector two), or more concisely, a physical address of (0, 7, 2). The terms “address” and “pointer” are used interchangeably herein.
Alternatively, a given sector may be identified by a “logical sector address.” Each logical sector address is a single number rather than a triplet of numbers. The logical address of a sector corresponds to the number of sectors between the addressed sector and the “first” sector on the disk
10
along some specified path which traverses all available sectors in order. The first sector, known as “sector zero,” is often located at a physical sector address of (0, 0, 1). One common traversal path begins at logical sector zero, traverses the sectors in cylinder zero of head zero, traverses the sectors of cylinder zero of head one, proceeds thus through cylinder zero on each successive head, proceeds to the sectors of cylinder one of head zero, and continues in like manner. However, other disk traversal paths are also used.
Disks are also classified by rules governing the physical organization of data on the disk. Many disks mold the available space into one or more “partitions” by a “partition table” located on the disk. For instance, MACINTOSH® computers utilize a partition table having a composition that is specifically adapted for use with the MACINTOSH operating system (MACINTOSH is a registered trademark of Apple Computer, Inc.). Many SUN® workstation computers utilize a partition table composition that is specifically adapted for use with the SunOS® File System (SUN and SunOS are registered trademark of Sun Microsystems, Inc.). Other examples abound; different partition table compositions are almost as common as different operating systems and different file systems, which number in the hundreds.
Unfortunately, different partition table compositions are usually incompatible. Detailed methods which correctly modify the contents of a first partition table will often scramble the contents of a second partition table if the first and second tables use different composition rules. A detailed method for reducing the number of disk sectors in a MACINTOSH partition, for instance, is likely to be of little help in shrinking a SunOS partition, and may even cause data loss if applied to the SunOS partition table.
One partition table composition, denoted herein as the “IBM-compatible” partition table, is found on the disks used in many IBM® personal computers and IBM-compatible computers (IBM is a registered trademark of International Business Machines Corporation). IBM-compatible partition tables may be used on both floppies and hard disks, and they may be used with magnetic disks, optical disks, and disks employing other storage media. IBM-compatible partition tables may also be used with a variety of disk sector addressing schemes, including without limitation schemes that employ traversal paths different from the path described above and schemes which assign logical sector addresses that start over again at zero for each partition on the disk.
As shown in
FIG. 2
, an IBM-compatible partition table
32
includes an Initial Program Loader (“IPL”) identifier
34
, four primary partition identifiers
36
, and a boot identifier
38
. As shown in
FIG. 3
, each partition identifier
36
includes a boot indicator
40
to indicate whether the partition in question is bootable. At most one of the partitions in the set of partitions defined by the partition table
32
is bootable at any given time.
Each partition identifier
36
also includes a starting address
42
, which is the physical sector address of the first sector in the partition in question, and an ending address
44
, which is the physical sector address of the last sector in the partition. A sector count
46
holds the total number of disk sectors in the partition. A boot sector address
48
holds the logical sector address corresponding to the physical starting address
42
. On disks having more than 1024 cylinders, the starting address
42
and the ending address
44
contain predetermined maximum values if the actual values are too large to store in the space given in the partition table
32
; the actual values can be derived from the sector count
46
and the boot sector address
48
.
Some IBM-compatible computer systems allow “logical partitions” as well as the primary partitions just described. All logical partitions are contained within one primary partition; a primary partition which contains logical partitions is also known as an “extended partition.” Logical partitions are represented by one or more lists of partition identifiers
36
. Each list is attached in conventional fashion to one of the partition identifiers P
1
, P
2
, P
3
, or P
4
. Thus, the set of partitions defined by an IBM-compatible partition tab

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