Tape header format having efficient and robust codeword interleave designation (CWID) protection

Patent metadata

Field	Value
Publication number	US-9548760-B2
Application number	US-201514726522-A
Country	US
Kind code	B2
Filing date	May 30, 2015
Priority date	Aug 26, 2013
Publication date	Jan 17, 2017
Grant date	Jan 17, 2017

Abstract

In one embodiment, a computer program product for providing header protection in magnetic tape recording includes a computer readable storage medium having program instructions embodied therewith, the program instructions readable by a processor to cause the processor to: calculate or obtain, by the processor, codeword interleave designation (CWID) parity for all CWIDs in a codeword interleave (CWI) set header, the CWID parity including error correction coding (ECC) parity, and store, by the processor, the CWID parity to a magnetic tape in one or more fields which are repeated for each CWI header in the CWI set header without using reserved bits in the CWI set header to store the CWID parity. Other systems and methods for providing header protection in magnetic tape recording are described in more embodiments.

First claim

What is claimed is:

1. A computer program product for providing header protection in magnetic tape recording, the computer program product comprising a non-transitory computer readable storage medium having program instructions embodied therewith, the program instructions readable by a processor to cause the processor to:
calculate or obtain, by the processor, codeword interleave designation (CWID) parity for all CWIDs in a codeword interleave (CWI) set header, the CWID parity comprising error correction coding (ECC) parity; and
store, by the processor, the CWID parity to a magnetic tape in one or more fields which are repeated for each CWI header in the CWI set header without using reserved bits in the CWI set header to store the CWID parity.

2. The computer program product as recited in claim 1 , wherein the program instructions are further readable by the processor to:
write, by the processor, a CWI set on the magnetic tape, the CWI set comprising a plurality of CWIs being equal to a number of tracks on the magnetic tape, wherein a data set comprises a plurality of CWI sets; and
provide, by the processor, the CWI set header for the CWI set, the CWI set header comprising a CWI header for each CWI in the CWI set, each CWI header comprising at least a CWI Designation (CWID) which indicates a location of the CWI within the data set.

3. The computer program product as recited in claim 2 , wherein each CWI header is 12 bytes in length (byte 0 to byte 11 ), and wherein each CWI header comprises:
an amble flag (AF), an adjacent wrap toggle (AWT) field, and a data set identifier fragment (DSIF) stored in byte 0 (H 0 );
an absolute codeword object set sequence number (ACN) stored in bytes 1 and 2 (H 1 and H 2 );
a CWID stored in bytes 2 and 3 (H 2 and H 3 );
reserved bits in bytes 4 and 5 (H 4 and H 5 );
a write pass identifier (WPI) stored in bytes 6 , 7 , 8 , and 9 (H 6 , H 7 , H 8 , and H 9 ); and
header parity stored in bytes 10 and 11 (HA and HB).

4. The computer program product as recited in claim 3 , wherein the one or more repeated fields which are used to store the CWID parity comprise at least one of: AF, AWT, DSIF, and ACN.

5. The computer program product as recited in claim 4 , wherein the magnetic tape has 32 tracks, wherein the CWID parity is stored as 8 bits on all 32 tracks of the magnetic tape, wherein the AF, AWT, and DSIF are stored in 11 bits on 16 of the 32 tracks of the magnetic tape, and wherein ACN is stored in 11 bits on another 16 tracks of the magnetic tape.

6. The computer program product as recited in claim 5 , wherein the CWID parity is stored as one symbol having a Reed-Solomon (RS) code symbol size of 8 bits, and wherein the CWIDs occupy 13 bits on each track of the magnetic tape and are mapped into two symbols with three virtual bits for RS encoding.

7. The computer program product as recited in claim 4 , wherein the CWID parity is stored as 19 bits on L of a total M tracks of the magnetic tape, wherein L<M, and wherein the AF, AWT, DSIF, and ACN are stored on another M-L tracks of the magnetic tape.

8. The computer program product as recited in claim 4 , wherein the CWID parity is stored as 16 bits on L of a total M tracks of the magnetic tape, wherein L<M, wherein the AF, AWT, DSIF, and ACN are stored on 19 bits of another M-L tracks of the magnetic tape, and wherein AF and AWT are stored on an additional 3 bits of the L tracks of the magnetic tape.

9. The computer program product as recited in claim 8 , wherein the CWID parity is stored as two symbols having a Reed-Solomon (RS) code symbol size of 8 bits, and wherein the CWIDs occupy 13 bits of each track of the magnetic tape and are mapped into two symbols with three virtual bits for RS encoding.

10. The computer program product as recited in claim 4 , wherein the CWID parity is stored as 14 bits on L of a total M tracks of the magnetic tape, wherein L<M, wherein the AF, AWT, DSIF, and ACN are stored on 19 bits of another M-L tracks of the magnetic tape, and wherein AF and AWT are stored on an additional 5 bits of the L tracks of the magnetic tape.

11. The computer program product as recited in claim 10 , wherein the CWID parity is stored as two symbols having a Reed-Solomon (RS) code symbol size of 7 bits, and wherein the CWIDs occupy 13 bits of each track of the magnetic tape and are mapped into two symbols with one virtual bit for RS encoding.

12. The computer program product as recited in claim 4 , wherein the CWID parity is stored as 7 bits on each track of the magnetic tape, wherein the AF, AWT, and DSIF are stored on 12 bits of L of a total M tracks of the magnetic tape, wherein L<M, and wherein ACN is stored in 12 bits of another M-L tracks of the magnetic tape, and wherein the CWID parity is stored as one symbol having a Reed-Solomon (RS) code symbol size of 7 bits, and wherein the CWIDs occupy 13 bits of each track of the magnetic tape and are mapped into two symbols with one virtual bit for RS encoding.

13. A system for providing header protection in magnetic tape recording, the system comprising a processor and logic integrated with and/or executable by the processor, the logic being configured to:
calculate or obtain codeword interleave designation (CWID) parity for all CWIDs in a codeword interleave (CWI) set header, the CWID parity comprising error correction coding (ECC) parity; and
store the CWID parity to a magnetic tape in one or more fields which are repeated for each CWI header in the CWI set header without using reserved bits in the CWI set header to store the CWID parity.

14. The system as recited in claim 13 , wherein the logic is further configured to:
write a CWI set on the magnetic tape, the CWI set comprising a plurality of CWIs being equal to a number of tracks on the magnetic tape, wherein a data set comprises a plurality of CWI sets; and
provide the CWI set header for the CWI set, the CWI set header comprising a CWI header for each CWI in the CWI set, each CWI header comprising at least a CWI Designation (CWID) which indicates a location of the CWI within the data set,
wherein each CWI header is 12 bytes in length (byte 0 to byte 11 ), and wherein each CWI header comprises:
an amble flag (AF), an adjacent wrap toggle (AWT) field, and a data set identifier fragment (DSIF) stored in byte 0 (H 0 );
an absolute codeword object set sequence number (ACN) stored in bytes 1 and 2 (H 1 and H 2 );
a CWID stored in bytes 2 and 3 (H 2 and H 3 );
reserved bits in bytes 4 and 5 (H 4 and H 5 );
a write pass identifier (WPI) stored in bytes 6 , 7 , 8 , and 9 (H 6 , H 7 , H 8 , and H 9 ); and
header parity stored in bytes 10 and 11 (HA and HB),

wherein the one or more repeated fields which are used to store the CWID parity comprise at least one of: AF, AWT, DSIF, and ACN.

15. The system as recited in claim 14 , wherein the magnetic tape has 32 tracks and the CWID parity is stored as 8 bits on all 32 tracks of the magnetic tape, the AF, AWT, and DSIF are stored in 11 bits on 16 of the 32 tracks of the magnetic tape, and ACN is stored in 11 bits on another 16 tracks of the magnetic tape; or wherein the CWID parity is stored as 19 bits on L of a total M tracks of the magnetic tape, the AF, AWT, DSIF, and ACN are stored on another M-L tracks of the magnetic tape, and M=32 and L=12 or 16.

16. The system as recited in claim 14 , wherein the CWID parity is stored as 16 bits on L of a total M tracks of the magnetic tape, wherein L<M, wherein the AF, AWT, DSIF, and ACN are stored on 19 bits of another M-L tracks of the magnetic tape, wh

Assignees

• IBM

Inventors

• Cideciyan Roy D
• Hutchins Robert A
• Mittelholzer Thomas
• Tanaka Keisuke

Classifications

• G11B20/1833 Primary

  by adding special lists or symbols to the coded information (G11B20/1806, G11B20/1866 take precedence) · CPC title

• H03M13/2948

  Iterative decoding (H03M13/2957 takes precedence) · CPC title

• G06F11/1076

  Parity data used in redundant arrays of independent storages, e.g. in RAID systems · CPC title

• H03M13/2945

  using at least three error correction codes (H03M13/2957 takes precedence) · CPC title

• H03M5/00

  Conversion of the form of the representation of individual digits · CPC title