Tape drive emulation system for a disk drive

• US 5,297,124 A
• Filed: 04/24/1992
• Issued: 03/22/1994
• Est. Priority Date: 04/24/1992
• Status: Expired due to Fees

• Current Assignee: Miltope Corporation (Singapore Technologies Engineering Limited)
• Original Assignee: Miltope Corporation (Singapore Technologies Engineering Limited)
• Inventors: Plotkin, Barry, Ginsburg, Daniel C.
• Primary Examiner(s): ARGENBRIGHT, TONY MICHAEL
• Application Number:
  US07/874,585
• Time in Patent Office: 697 Days
• Field of Search: 369/32, 360/15, 360/72.2, 360/32, 360/48, 395/500, 364/927.81
• US Class Current: 360/49
• 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 3/0664 at device level, e.g. emulation of a storage device or system
• CPC Class Codes: G06F 3/0676 Magnetic disk device
• CPC Class Codes: G11B 20/1262 with more than one format/standard, e.g. conversion from CD-audio format to R-DAT format

Abstract

The invention relates to an emulator system which allows a disk drive to transparently emulate a tape drive. The system converts sequential format tape records into block format disk records and visa-versa. Identification and conversion information for each of the data records are stored in directory located on the outermost sectors of the disk. Within each directory are a plurality of entries each containing four fields: TAPE RECORD NUMBER (TRN); DISK START ADDRESS (DSA); WORD COUNT (WC); and FLAG. These fields contain all of the necessary information required to map a tape formatted data record to a disk and thereafter retrieve the data record from the disk and convert it back to tape format.

Claims

1. A tape drive emulation system, for allowing a disk drive device, connected to a host computer through a tape drive interface, to transparently emulate a tape drive device, comprising:

first recording means for recording a master directory containing a plurality of sequentially numbered entries to an area on a disk, each of said sequentially numbered entries corresponding to a sequentially numbered tape data record, each of said entries containing a DISK START ADDRESS field;

converting means for converting said tape data record to a disk format data record; and

second recording means for recording said disk format data record to said disk starting at an address specified by said DISK START ADDRESS field of said corresponding entry.

2. A tape drive emulation system for a disk drive device as recited in claim 1 wherein said entries further include a FLAG field, said FLAG field for indicating the current status of said corresponding disk data record.

3. A tape drive emulation system for a disk drive device as recited in claim 1 wherein said entries further include a WORD COUNT field for storing the length of said corresponding data record.

4. A tape drive emulation system for a disk drive device as recited in claim 1 wherein said first recording means additionally records a redundant directory identical to said master directory.

5. A tape drive emulation system for a disk drive device as recited in claim 1 wherein said disk is a magnetic disk.

6. A tape drive emulation system for a disk drive device as recited in claim 1 wherein said disk is a rewritable optical disk.

7. A tape drive emulation system as recited in claim 1 wherein said system is plug-compatible with said tape drive interface.

8. A method for mapping tape format data records to a disk, comprising the steps of:

recording a master directory to said disk, said master directory comprised of a plurality of sequentially numbered entries, each of said entries corresponding a sequentially numbered tape data record;

storing a disk start address for each of said tape data records in said corresponding entry;

converting said tape data records to disk format data records;

writing said disk format data records to said disk at said disk start address stored in said corresponding entry; and

setting a flag within said corresponding entry to indicate a valid data record.

9. A method for mapping tape format data records to a disk as recited in claim 8, further comprising the steps of:

sequentially traversing said entries on said disk in response to a tape read command;

sending an inter-record gap interrupt signal to a tape drive interface after each of said entries is traversed;

checking said flag within each of said entries to determine if said corresponding data record is valid;

reading said data record from said disk beginning at said start address stored in said entry; and

converting said data record from disk format data to tape format data.

10. A method for mapping tape format data records to a disk drive as recited in claim 8, further comprising the step of setting said flag to indicate erased condition in response to an erase command.

11. A method for mapping tape format data records to a disk drive as recited in claim 8, further comprising the step of recording a redundant directory to said disk, said redundant directory being identical to said master directory.

12. A method for mapping tape format data records to a disk drive as recited in claim 8 wherein said tape data records are variable in length.