In-place disk partition canonization and storage optimization

Details In-place disk partition canonization and storage optimization In-place disk partition canonization and storage optimization

1998-07-15

2001-02-06

Alam, Hosain T. (Department: 2172)

Data processing: database and file management or data structures

Database design

Data structure types

C711S112000, C711S113000, C711S173000

Reexamination Certificate

active

06185575

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to in-place manipulation of a computer disk partition without archiving or destroying user data, and more particularly to in-place canonization and storage optimization of a partition which holds an advanced file system.
TECHNICAL BACKGROUND OF THE INVENTION
Computers utilize a wide variety of disks as storage media for user data. Disk technologies currently provide optical disks, magnetic disks, hard disks, floppy disks, and removable disks, and new disk technologies are being actively researched and developed. Indeed, some disks used by computers in the future may be cubical or some other shape rather than flat and circular.
FIG. 1
illustrates a disk
100
attached to a disk drive
102
. The disk
100
illustrates physical characteristics of both floppies and hard disks; flash memory, cubical disks or other disks may appear in different configurations than the one shown here. The disk
100
contains a number of concentric data cylinders such as the cylinder
104
. The cylinder
104
contains several data sectors, including sectors
106
and
108
. The sectors
106
and
108
are located on an upper side
110
of the disk
100
; additional sectors may be located on a lower side
112
of the disk
100
. The sides
110
,
112
of the disk
100
define a platter
114
. A hard disk may contain several platters. The upper side
110
of the disk
100
is accessed by a head
116
mounted on an arm
118
secured to the drive
102
. Optical or cubical disks may be accessed by other means, such as photoemitters or photoreceptors, and flash memory or other memory disks are accessed by electronic circuits familiar to those of skill in the art.
A given sector on the disk
100
may be identified by specifying a head, a cylinder, and a sector within the cylinder. A triplet specifying the head number, cylinder number, and sector number in this manner is known as a “physical sector address.” Alternatively, a given sector may be identified by a logical sector address, which is a single number rather than a triplet of numbers.
Many disks mold the available space into one or more partitions by using a partition table located on the disk. A wide variety of partitions are used, and more partition types will no doubt be defined over time. Many partitions reside on a single disk, but some use volume sets, stripe sets, mirror sets, or other approaches to store a single partition's data on more than one disk. A partial list of current partitions and their associated file systems is given in U.S. patent application Ser. No. 08/834,004, filed Apr. 12, 1997, and incorporated here by reference. The list includes a variety of 12-bit, 16-bit, and 32-bit FAT file systems and numerous other file systems.
A file system of particular interest here is the NT File System (“NTFS”). Discussions of NTFS are provided in “Inside the Windows NT File System”, by Helen Custer, ISBN 1-55615-660-X, as well as in marketing and technical materials available in hard copy and on the Internet from Microsoft Corporation and other sources. Those of skill in the art will note that these discussions sometimes involve unimplemented specifications or mere speculations.
NTFS contains advanced file system features which make it more complex or difficult to manipulate NTFS partitions than it is to manipulate partitions organized by many existing FAT file systems. More precisely, NTFS combines features such as the use of a database paradigm to support indexing of file attributes; multiple data streams per file; blurring of the distinction between system and user areas; recoverability by use of a log; recoverability by use of transactions; support for large disks; security descriptors constraining access to file objects; Unicode names; support for POSIX features such as links; bad cluster remapping; caching support; virtual memory support; system structure compression; balanced tree directory structures; support for volume spanning, volume sets, stripe sets, mirror sets, and other features which divide a file system's contents between disks or partitions; and/or a relocatable system area. “Attributes” are also known as “data streams”; some advanced file systems allow a single file to hold multiple data streams.
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 a wide variety of disks, with a variety of partition and file system types, in a variety of ways. In particular, the partition table format may be changed without necessarily changing file system formats, and vice versa.
As shown in
FIG. 2
, one version of an IBM-compatible partition table
200
includes an Initial Program Loader (“IPL”) identifier
202
, four primary partition identifiers
204
, and a boot identifier
206
. As shown in
FIG. 3
, each partition identifier
204
includes a boot indicator
300
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
200
is bootable at any given time but “boot management” tools are commercially available to facilitate booting from different partitions.
Each partition identifier
204
also includes a starting address
302
, which is the physical sector address of the first sector in the partition in question, and an ending address
304
, which is the physical sector address of the last sector in the partition. A sector count
306
holds the total number of disk sectors in the partition. A boot sector address
308
holds the logical sector address corresponding to the physical starting address
302
. Additional partition information may be stored in a disk administrator utility or other location outside the partition table, or in an enhanced partition table, particularly when partitions are allowed to span disks.
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.”
Each partition identifier
204
also includes a system indicator
310
. The system indicator
310
identifies the type of file system contained in the partition, which in turn defines the physical arrangement of data that is stored in the partition on the disk
100
(FIG.
1
). For instance, the system indicator may indicate that data is organized in the partition according to some version of NTFS, with multiple data streams, a relocatable system area, and other features noted above. System indicator values not recognized by a particular operating system are treated as designating an unknown file system. The file system associated with a specific partition of the disk
100
determines the format in which data is stored in the partition, namely, the physical arrangement of user data and of file system structures in the portion of the disk
100
that is delimited by the starting address
302
and the ending address
304
of the partition in question. At any given time, each partition thus contains at most one type of file system.
An operating system manages access, not only to the disk
100
, but to other computer resources as well. Resources typically managed by the operating system include one or more disks and disk drives, memory (RAM and/or ROM), micro-processors, and I/O devices such as a keyboard, mouse, screen, printer, tape drive, modem, serial port, parallel port, or network port.
It is sometimes desirable to alter the contents of a partition in-place without copying all necessary user and system data off the disk to a temporary storage location such as a tape or another disk and using FDISK or a similar tool. Inventions for in-place partition manipulation without destroying user data are described in U.S. Pat. Nos. 5,675,769 and 5,706,472, and in

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