Method and system for storing file system state information in multiple sectors based on update frequency

• US 5,873,118 A
• Filed: 09/01/1994
• Issued: 02/16/1999
• Est. Priority Date: 08/29/1989
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Letwin, James Gordon
• Primary Examiner(s): Swann, Tod R.
• Assistant Examiner(s): Thai, Tuan V.
• Application Number:
  US08/299,511
• Time in Patent Office: 1,629 Days
• Field of Search: 395/425, 395/600, 395/427, 364/DIG. 1, 364/DIG. 2, 711/154, 711/156, 707/202, 707/205
• US Class Current: 711/156
• CPC Class Codes: G06F 16/13 File access structures, e.g. distributed indices arrangements of input from, or output to, record carriers G06F3/06
• CPC Class Codes: G06F 16/1794 Details of file format conversion
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0643 Management of files
• CPC Class Codes: G06F 3/0674 Disk device
• CPC Class Codes: G11B 20/1252 for discontinuous data, e.g. digital information signals, computer programme data
• CPC Class Codes: G11B 27/329 on a disc [VTOC]
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99956 File allocation

Abstract

A method and system for storing file system state information within sectors of the file system. File system information includes pointers to top-level file system structures, such as free space bitmaps, a bad block list, a directory block band, and a root directory. The system classifies the file system state information into two groups: frequently-updated information and infrequently-updated information. The two groups are stored on separate sectors. Thus, the frequently updated information can be updated without rewriting the infrequently updated information. Because the infrequently updated information is not rewritten, the risk of this information being corrupted is significantly reduced.

Claims

1. A method in a computer system for storing information describing a state of a file system, the information being divided into writable information that is frequently updated and read information that is infrequently updated on a file storage device, wherein said file storage device can be both read from and written to multiple times, the method comprising the steps of:

storing said read information that is infrequently updated on a first sector of said file storage device, a sector being a unit of accessibility such that when updating any information of said sector, all the information of said sector is overwritten;

storing said writable information that is frequently updated on a second sector of said file storage device; and

updating said writable information stored in said second sector separately without overwriting said read information stored on said first sector in order to minimize errors within said first sector.

2. The method of claim 1 wherein the infrequently updated information includes a pointer to sector allocation information, a pointer to a directory block band, or a pointer to a root directory.

3. The method of claim 1 wherein the infrequently updated information is read-only information.

4. The method of claim 1 wherein the information describing the state of the file system is super block information.

5. A computer system for storing information describing a state of a file system, the information being divided into frequently updated information and infrequently updated information, wherein said infrequently updated information being categorized as read information and said frequently updated information being categorized as writable information, comprising:

a file storage device that can be read from and written to multiple times;

means for storing said infrequently updated information on a first sector of said file storage device wherein a sector being a unit of accessibility such that when updating any information of said sector, all the information of said sector is overwritten; and

means for storing said frequently updated information on a second sector of said file storage device so that said writable information stored in said second sector is updated without overwriting said read information stored on said first sector of said file storage device in order to minimize errors within said first sector.

6. The system of claim 5 wherein the infrequently updated information includes a pointer to sector allocation information, a pointer to a directory block band, or a pointer to a root directory.

7. A computer-readable medium containing instructions for causing a file system within a computer system to store state information describing a state of the file system, the file system having a file storage device that is divided into sectors for storing information, a sector being a unit of accessibility such that when updating any information of said sector, all the information of said sector is overwritten, wherein each sector of said file storage device capable of being read from and written to multiple times, by:

categorizing the state information as either infrequently updated information or frequently updated information wherein said infrequently updated information is read information and said frequently updated information is writable information;

storing the state information categorized as infrequently updated information on a first sector of said file storage device;

storing the state information categorized as frequently updated information on a second sector of said file storage device; and

updating the state information categorized as frequently updated information by overwriting state information stored on said second sector without overwriting said state information stored on said first sector, whereby said overwriting of said state information categorized as infrequently updated information is minimized thereby reducing possibility of corrupting said state information categorized as infrequently updated information by frequent overwriting.

8. The computer-readable medium of claim 7 wherein the state information is super block information.

9. The computer-readable medium of claim 7 wherein the state information includes a pointer to sector allocation information.

10. The computer-readable medium of claim 7 wherein the state information includes a pointer to a directory block band.

11. The computer-readable medium of claim 7 wherein the state information includes a pointer to a root directory.