Computer partition manipulation during imaging

Details Computer partition manipulation during imaging Computer partition manipulation during imaging

1998-08-15

2001-06-26

Ellis, Kevin L. (Department: 2185)

Electrical computers and digital processing systems: memory

Storage accessing and control

Memory configuring

C711S112000, C711S165000

Reexamination Certificate

active

06253300

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to on-the-fly manipulation of computer storage device partitions, and more particularly to changing the sector count and/or cluster size of a partition while otherwise replicating the partition.
TECHNICAL BACKGROUND OF THE INVENTION
Some Terminology
Computer hard disks and other computer storage devices hold digital data which represents numbers, names, dates, texts, pictures, sounds, and other information used by businesses, individuals, government agencies, and others. To help organize the data, and for technical reasons, many computers divide the data into drives, partitions, directories, and files. The terms “file” and “directory” are familiar to most computer users, and most people agree on their meaning even though the details of written definitions vary.
However, the terms “partition” and “drive” have different meanings even when the context is limited to computers. According to some definitions, a partition is necessarily limited to one storage device but a “file system” may include one or more partitions on one or more disks. 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.
As used here, a “partition” is a region on one or more storage devices which is (or can be) formatted to contain one or more files or directories. A partition may be empty. A partition may also be in active use even without any directories, file allocation tables, bitmaps, or similar file system structures if it holds a stream or block of raw data. Each formatted partition is tailored to a particular type of file system, such as the Macintosh file system, SunOS file system, Windows NT File System (“NTFS”), NetWare file system, or one of the MS-DOS/FAT file systems (MACINTOSH is a trademark of Apple Computer, Inc.; SUNOS is a trademark of Sun Microsystems, Inc.; WINDOWS NT and MS-DOS are trademarks of Microsoft Corporation; NETWARE is a trademark of Novell, Inc.). Partition manipulation may include manipulation of file system data within the partition. A file system need not fill the partition which holds it, either in the sense that all sectors within the partition are used by the file system or in the sense that all sectors within the partition are recognized by the file system as being present.
“Drive” is sometimes used interchangeably with “partition,” especially in references to logical drive C: or another logical drive holding the operating system on so-called Wintel machines. But “drive” may also refer to a single physical storage device such as a magnetic hard disk or a CD-ROM drive. To reduce confusion, “drive” will normally be used here to refer only to storage devices, not to partitions. Thus, it is accurate to note that a partition often resides on a single drive but may also span drives, and a drive may hold one or more partitions.
Partition Manipulation Generally
It is often useful to manipulate partitions by creating them, deleting them, moving them, copying them, changing their size, changing the cluster size used by their file systems, and performing other operations. A number of tools for manipulating partitions are commercially available, including the FDISK program and the PartitionMagic® program (PARTITIONMAGIC is a registered trademark of PowerQuest Corporation). Partition manipulation is discussed in detail in U.S. Pat. Nos. 5,675,769 and 5,706,472, incorporated herein, and in other references.
Disk Imaging Generally; A First Imaging Method
It is also useful to copy partitions in groups to create archive copies or to configure additional storage devices. For instance, backup programs have long been available to copy every file in a partition, every file in a group of partitions, or every sector (used or not) on a disk to another storage device such as a secondary disk or tape drive on the same computer or a connected computer such as a file server.
Various programs have become available for copying or “imaging” a group of partitions stored on a source disk drive. Imaging programs in general allow multiple partitions to be copied. The first, and simplest, imaging method (“Method A”) used is a “file-by-file” approach that creates a copy of every single file that is found in one or more source partition(s). The copy can be stored to temporary storage as an “image file,” or the intermediate storage step can easily be dispensed with so the imaging is performed directly to create another disk image (on one or more hard drives, simultaneously or sequentially).
If the copy is to be stored in an image file, it can optionally be compressed prior to storage, and then decompressed at the appropriate stage while creating a new disk image. Compression operates on the data being stored to reduce redundancy by run-length encoding, for instance. An image file may pack clusters, compress data, or both. An image file, unlike a partition, stores data in a form not recognized by conventional file system software. For instance, user data clusters may be packed, so the cluster numbers or other pointers in the file system structures in an image file do not necessarily point to the current (packed) location of the data clusters in question; the clusters are unpacked and restored to their expected relative locations when data from the image file is copied to a target disk to create a partition there. “Target” and “destination” are used interchangeably herein.
When a new image is to be created, the partition size(s) of the destination partition(s) is determined and the destination partition(s) is quickly formatted for the appropriate file system and at the chosen size. Then, each file is copied, one at a time, to the new image. All directory and other system updates occur as each file is copied. At the option of the implementer of this method, any type of disk caching scheme can (and should) be used to group disk updates to reduce disk-head movement, which in turn will reduce the time required to complete the operation.
Even with caching, however, file-by-file copying often requires significant disk head movement for at least two reasons. First, in many cases the disk head must move from one contiguous group of sectors to the next contiguous group as it reads a given file. This head movement can be minimized for multiple reads of a given file by defragmenting the file, but defragmentation itself generally requires head movement and data movement. Second, in many cases the disk head moves each time a new file is opened for reading, since the end of one file is often not contiguous with the start of the next file. In addition, file-by-file copy programs often make the disk head(s) jump back and forth between a directory containing information such as the file names and a user data area which holds file contents.
Accordingly, some disk imaging programs do not copy user data file-by-file, but instead copy data cluster-by-cluster or sector-by-sector. All clusters or sectors are copied in some cases, and only used clusters or sectors are copied in others. As explained further below, although cluster-by-cluster and sector-by-sector approaches often require less head movement than file-by-file approaches, imaging and partition manipulation (such as partition resizing or cluster resizing) are separate, sequential and often time-consuming steps in conventional systems.
Partition Manipulation with a Second Disk Imaging Method
A second method (“Method B”) of disk imaging, which is somewhat harder to implement than Method A, takes a sector-by-sector approach. One version of Method B copies all used sectors of the source hard-disk partition(s). The copy can be stored to temporary storage in the form of an image file stored on one or more disks, or the intermediate storage step can be dispensed with so the imaging is performed directly to create another disk image on one or more hard drives, simultaneously or sequentially.
To reduce the amount of data transferred, it is possible to use a version of Method B which copies fewer sectors. This

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