Tape drive emulator for removable disk drive

• US 6,128,698 A
• Filed: 08/04/1997
• Issued: 10/03/2000
• Est. Priority Date: 08/04/1997
• Status: Expired due to Term

• Current Assignee: Tandberg Data Corporation
• Original Assignee: Exabyte Corporation (MidgardXXI, Inc.)
• Inventors: Georgis, Steven P.
• Primary Examiner(s): Cabeca, John W.
• Assistant Examiner(s): Namazi, Mehdi
• Application Number:
  US08/905,326
• Time in Patent Office: 1,156 Days
• Field of Search: 395/500, 369/84, 369/59, 711/118, 360/15, 360/61
• US Class Current: 711/111
• CPC Class Codes: G06F 11/1456 Hardware arrangements for backup
• CPC Class Codes: G06F 3/0607 by facilitating the process of upgrading existing storage systems, e.g. for improving compatibility between host and storage device
• CPC Class Codes: G06F 3/0661 Format or protocol conversion arrangements
• CPC Class Codes: G06F 3/0664 at device level, e.g. emulation of a storage device or system
• CPC Class Codes: G06F 3/0674 Disk device
• CPC Class Codes: G06F 3/0682 Tape device

Abstract

A tape drive emulator (30) is between a host computer (40) and a removable disk drive (22) and appears to the host computer 40 as a sequential storage system, e.g., a tape drive. However, the tape drive emulator (30) processes the data obtained from or applied to host computer 40 so that the data can be communicated to removable disk drive 22 in a manner compatible with a conventional removable disk drive. Yet in so doing, tape drive emulator 30 imposes on the data (1) an data organization, imperceptible to disk drive 22, for rendering the data expressable and locatable in a tape drive format, and (2) an additional degree of error correction that provides enhanced data integrity necessary for data backup/restore operations.

Claims

1. A data storage system which connects to a host computer for performing one of a data backup operation and data restore operation, the data storage system comprising:

a disk drive which transduces information in a sector format with respect to a rotating disk,

a tape drive emulator connected between the disk drive and the host computer, the tape drive emulator interfacing with the host computer using a set of commands applicable to a tape drive, the tape drive emulator communicating data to and from the disk drive whereby the data is transduced relative to the disk in the sector format,

wherein the tape drive emulator generates a frame of data, the frame of data being recorded in a predetermined plural number of sectors on the disk, the frame of data having frame error correction bytes generated over the frame, the error correction bytes being sufficient to recover a sector of the disk not readable by the disk drive.

2. The system of claim 1, wherein the tape drive emulator generates plural frames of data, each of the frames of data being recording on the predetermined plural number of sectors on the disk, at least some of the frames serving as directory frames, the directory frames having stored therein references to storage locations on the disk of data delineators.

3. The system of claim 2, wherein the data delineators include one of logical block numbers, file marks, and set marks.

16. The system of claim 1, wherein the predetermined plural number of sectors is forty.

17. The system of claim 1, wherein error correction information is stored on two of the predetermined plural number of sectors.

18. The system of claim 1, wherein user data included in a frame corresponds to a buffer block of data generated by the tape drive.

33. The system of claim 1, wherein the disk is a rotating magnetic disk.

34. The system of claim 1, wherein the disk is a removable disk.

4. A data storage system which connects to a host computer for performing one of a data backup operation and data restore operation, the data storage system comprising:

a disk drive which transduces information on a rotating disk,

a tape drive emulator connected between the disk drive and the host computer, the tape drive emulator comprising;

a compression engine which compresses logical blocks obtained from the host computer;

a packer unit which packs compressed logical blocks into a buffer block;

an error correction encoder which generates error correction bytes over the buffer block; and

wherein the buffer block and error correction bytes are combined for transmission as a frame to the disk drive, the frame being recordable in a predetermined plural number of sectors on the disk drive.

5. The system of claim 4, wherein the error correction bytes are sufficient to recover a sector of the disk not readable by the disk drive.

6. The system of claim 4, wherein the tape drive emulator further comprises a header generator which generates header bytes for inclusion in the frame, the header bytes including frame identifying information.

19. The system of claim 4, wherein the predetermined plural number of sectors is forty.

20. The system of claim 4, wherein error correction information is stored on two of the predetermined plural number of sectors.

21. The system of claim 4, wherein user data included in a frame corresponds to a buffer block of data generated by a the tape drive.

35. The system of claim 4, wherein the disk is a rotating magnetic disk.

36. The system of claim 4, wherein the disk is a removable disk.

7. A method of storing computer data on a rotating magnetic disk, the method comprising:

obtaining logical blocks of data from a host computer;

assembling the logical blocks into a buffer block, the buffer block having a size equivalent to a first predetermined number of sectors of the disk;

generating error correction bytes for the buffer block and adding the error correction bytes to the buffer block to form a frame, the frame having a size equivalent to a second predetermined number of sectors of the disk; and

recording the frame on the disk.

8. The method of claim 7, further comprising generating a frame header and including the frame header in the buffer block, the error correction bytes being generated over the buffer block including the frame header.

9. The method of claim 7, further comprising generating a CRC bytes for the buffer block and including the CRC bytes in the buffer block, the error correction bytes being generated over the buffer block including the CRC bytes.

10. The method of claim 7, further comprising compressing the logical blocks prior to assembling the logical blocks into the buffer block.

11. A tape drive emulator connected between a removable disk drive and a host computer, the tape drive emulator comprising:

a compression engine which compresses logical blocks obtained from the host computer;

a packer unit which packs compressed logical blocks into a buffer block;

an error correction encoder which generates error correction bytes over the buffer block; and

wherein the buffer block and error correction bytes are combined for transmission as a frame to the disk drive, the frame being recordable in a predetermined plural number of sectors on the disk drive.

12. The apparatus of claim 11, wherein the error correction bytes are sufficient to recover a sector of the disk not readable by the disk drive.

13. The apparatus of claim 11, wherein the tape drive emulator further comprises a header generator which generates header bytes for inclusion in the frame, the header bytes including frame identifying information.

14. The apparatus of claim 11, wherein the frame serves as a directory frame, the directory frame having stored therein references to storage locations on the disk of data delineators.

15. The apparatus of claim 14, wherein;

the data delineators include one of logical block numbers, file marks, and set marks.

22. The system of claim 11, wherein the predetermined plural number of sectors is forty.

23. The system of claim 11, wherein error correction information is stored on two of the predetermined plural number of sectors.

24. The system of claim 11, wherein user data included in a frame corresponds to a buffer block of data generated by a the tape drive.

25. A rotating information storage media formatted with sectors, a frame of data being recorded over a predetermined plural number of the sectors, the frame including user data and error correction information which permits recovery of the frame when a bad one of the sectors of the plural number of sectors is unreadable.

26. The media of claim 25, wherein the predetermined plural number of sectors is forty.

27. The media of claim 25, wherein the error correction information is stored on two of the predetermined plural number of sectors.

28. The media of claim 25, wherein the user data included in the frame corresponds to a buffer block of data generated by a the tape drive.

29. The media of claim 25, wherein some of the frames are directory frames.

30. A tape drive emulator which interfaces with a host computer using a set of commands applicable to a tape drive, the tape drive emulator generating a frame of data for recordation in a predetermined plural number of sectors on a rotating information storage media, the frame having frame error correction bytes generated over the frame, the error correction bytes being sufficient to recover a sector of the disk not readable by the disk drive.

31. The tape drive emulator of claim 30, wherein the tape drive emulator generates plural frames of data, each of the frames of data being recording on the predetermined plural number of sectors on the disk, at least some of the frames serving as directory frames, the directory frames having stored therein references to storage locations on the disk of data delineators.

32. The tape drive emulator of claim 31, wherein the data delineators include one of logical block numbers, file marks, and set marks.