Tape drive with intelligent selection of wrap / track for temporarily storing flushed data

• US 10,467,146 B1
• Filed: 05/02/2018
• Issued: 11/05/2019
• Est. Priority Date: 05/02/2018
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Miyamura, Tsuyoshi, Ogura, Eiji, Taketomi, Tomoko
• Primary Examiner(s): Vernbrugge, Kevin
• Application Number:
  US15/968,805
• Publication Number:
  US 20190340131A1
• Time in Patent Office: 552 Days
• Field of Search: None
• CPC Class Codes: G06F 12/0868 Data transfer between cache memory and other subsystems, e.g. storage devices or host systems
• CPC Class Codes: G06F 12/0891 using clearing, invalidating or resetting means
• CPC Class Codes: G06F 2212/213 Tape storage
• CPC Class Codes: G06F 2212/312 In storage controller
• CPC Class Codes: G06F 2212/462 Track or segment
• CPC Class Codes: G06F 2212/463 File
• CPC Class Codes: G06F 2212/70 Details relating to dynamic memory management
• CPC Class Codes: G11B 5/00817 on longitudinal tracks only, e.g. for serpentine format recording
• CPC Class Codes: G11B 5/78 Tape carriers

Abstract

A tape drive that can select one or more wraps from any available wraps on a tape medium for writing temporary data upon detecting a flush condition. The one or more wraps selected for writing temporary data can be selected from wraps otherwise reserved for normal writing operations. Selection of the one or more wraps for temporary writing may be based on multiple considerations, including proximity to the wrap of current data writing operations and tape medium degradation. The one or more wraps selected for writing temporary data may be selected with or without regard of their assigned read/write direction. Assigning wraps based on proximity and/or degradation can lead to certain operational advantages including reducing tape write head movement in the transverse direction and spreading tape medium wear more evenly across the surface of the tape medium.

Claims

1. A computer program product comprising:

a tape drive system including;

a buffer memory,

tape drive control logic,

a tape recording head for writing to-be-written data,

an elongated tape medium defining a transverse direction, with the tape medium being organized into a plurality of writing tracks adapted to have recorded thereon to-be-written data as written data,

a machine readable storage device, and

computer code stored on the machine readable storage device, with the computer code including instructions for causing a processor(s) set to perform operations including the following;

receiving, by a buffer memory, a stream of to-be-written data,

receiving, by the tape drive control logic, an identity of a first writing track of the plurality of writing tracks, with the first writing track being a track where to-be-written data is currently being permanently written as written data from the buffer memory to the tape medium by the tape recording head,

receiving, by the tape drive control logic, flush indication data indicating that a flush of the buffer memory needs to be performed,

responsive to the receipt of the buffer flush indication data, determining a second writing track of the plurality of writing tracks, with the second writing track being a writing track to be used in flushing to-be-written data from the buffer memory, and with the determination of the second writing being based, at least in part, upon a relative transverse direction proximity between the first writing track and the second writing track, and

flushing at least a portion of the buffer memory by writing to-be-written data from the buffer memory as temporary written data to the second writing track.

2. The product of claim 1 wherein the computer code further includes instructions for causing the processor(s) set to perform the following operations:

concurrent with flushing at least a portion of the buffer memory, receiving additional data from the stream of to-be-written data;

accumulating the additional data in the buffer memory; and

responsive to accumulating a predetermined size of data in the buffer, writing the accumulated data to the first writing track.

3. The product of claim 1 wherein the recursively re-written data is data required to complete a data segment stored as permanent data on the first writing track.

4. The product of claim 1 wherein:

the tape drive system is an RABF (recursively accumulating backhitchless flush) type tape drive system;

the plurality of data tracks are data wraps, with each wrap of the plurality of data wraps is designed to be permanently written in one of;

a forward direction or a reverse direction;

the plurality of data wraps are divided into a plurality of sub-sets called data bands; and

the determination of the second writing track is further based, at least in part, upon a constraint the second writing track must be in the same data band as the first writing track.

5. The product of claim 4 wherein:

the tape recording head is larger, in the transverse direction, than a transverse width of a data wrap; and

the tape medium further includes a plurality of guard wraps to prevent the tape recording head from compromising data on data tracks transversely adjacent to a data track currently being written.

6. The product of claim 5 wherein a first guard wrap of the plurality of guard wraps is located between the first writing track and the second writing track.

7. The product of claim 1 wherein:

half of the plurality of writing tracks are assigned for writing in the forward direction, with the other half assigned for writing in the reverse direction; and

the determination of the second writing track is further based, at least in part, on the assigned direction of the second track relative to a longitudinal direction of tape motion at a time when the flush indication data is received.

8. A computer program product comprising:

a tape drive system including;

a buffer memory,

tape drive control logic,

a tape recording head for writing to-be-written data,

an elongated tape medium defining a transverse direction, with the tape medium being organized into a plurality of writing tracks adapted to have recorded thereon to-be-written data as written data,

a machine readable storage device, and

computer code stored on the machine readable storage device, with the computer code including instructions for causing a processor(s) set to perform operations including the following;

receiving, by a buffer memory, a stream of to-be-written data,

receiving, by the tape drive control logic, an identity of a first writing track of the plurality of writing tracks, with the first writing track being a track where to-be-written data is currently being permanently written as written data from the buffer memory to the tape medium by the tape recording head,

receiving, by the tape drive control logic, flush indication data indicating that a flush of the buffer memory needs to be performed,

responsive to the receipt of the buffer flush indication data, determining a second writing track of the plurality of writing tracks, with the second writing track being a writing track to be used in flushing to-be-written data from the buffer memory, and with the determination of the second writing being based, at least in part, upon a degree of tape degradation of the plurality of writing tracks, and

flushing at least a portion of the buffer memory by writing to-be-written data from the buffer memory as temporary written data to the second writing track.

9. The product of claim 8 wherein the computer code further includes instructions for causing the processor(s) set to perform the following operations:

concurrent with flushing at least a portion of the buffer memory, receiving additional data from the stream of to-be-written data;

accumulating the additional data in the buffer memory; and

responsive to accumulating a predetermined size of data in the buffer, writing the accumulated data to the first writing track.

10. The product of claim 8 wherein the recursively re-written data is data required to complete a data segment stored as permanent data on the first writing track.

11. The product of claim 8 wherein:

the tape drive system is an RABF (recursively accumulating backhitchless flush) type tape drive system;

the plurality of data tracks are data wraps, with each wrap of the plurality of data wraps is designed to be permanently written in one of;

a forward direction or a reverse direction;

the plurality of data wraps are divided into a plurality of sub-sets called data bands; and

the determination of the second writing track is further based, at least in part, upon a constraint the second writing track must be in the same data band as the first writing track.

12. The product of claim 11 wherein:

the tape recording head is larger, in the transverse direction, than a transverse width of a data wrap; and

the tape medium further includes a plurality of guard wraps to prevent the tape recording head from compromising data on data tracks transversely adjacent to a data track currently being written.

13. The product of claim 12 wherein a first guard wrap of the plurality of guard wraps is located between the first writing track and the second writing track.

14. A computer program product comprising:

a tape drive system including;

a buffer memory,

tape drive control logic,

a tape recording head for writing to-be-written data,

an elongated tape medium defining a transverse direction, with the tape medium being organized into a plurality of writing tracks adapted to have recorded thereon to-be-written data as written data,

a machine readable storage device, and

computer code stored on the machine readable storage device, with the computer code including instructions for causing a processor(s) set to perform operations including the following;

receiving, by a buffer memory, a stream of to-be-written data,

receiving, by the tape drive control logic, an identity of a first writing track of the plurality of writing tracks, with the first writing track being a track where to-be-written data is currently being permanently written as written data from the buffer memory to the tape medium by the tape recording head,

receiving, by the tape drive control logic, flush indication data indicating that a flush of the buffer memory needs to be performed,

responsive to the receipt of the buffer flush indication data, determining a second writing track of the plurality of writing tracks, with the second writing track being a writing track to be used in flushing to-be-written data from the buffer memory, and with the determination of the second writing being based, at least in part, upon;

(i) a relative transverse direction proximity between the first writing track and the second writing track, and (ii) a degree of tape degradation of the plurality of writing tracks, and

flushing at least a portion of the buffer memory by writing to-be-written data from the buffer memory as temporary written data to the second writing track.

15. The product of claim 14 wherein the computer code further includes instructions for causing the processor(s) set to perform the following operations:

concurrent with flushing at least a portion of the buffer memory, receiving additional data from the stream of to-be-written data;

accumulating the additional data in the buffer memory; and

responsive to accumulating a predetermined size of data in the buffer, writing the accumulated data to the first writing track.

16. The product of claim 14 wherein the recursively re-written data is data required to complete a data segment stored as permanent data on the first writing track.

17. The product of claim 14 wherein:

the tape drive system is an RABF (recursively accumulating backhitchless flush) type tape drive system;

the plurality of data tracks are data wraps, with each wrap of the plurality of data wraps is designed to be permanently written in one of;

a forward direction or a reverse direction;

the plurality of data wraps are divided into a plurality of sub-sets called data bands; and

the determination of the second writing track is further based, at least in part, upon a constraint the second writing track must be in the same data band as the first writing track.

18. The product of claim 17 wherein:

the tape recording head is larger, in the transverse direction, than a transverse width of a data wrap; and

the tape medium further includes a plurality of guard wraps to prevent the tape recording head from compromising data on data tracks transversely adjacent to a data track currently being written.

19. The product of claim 18 wherein a first guard wrap of the plurality of guard wraps is located between the first writing track and the second writing track.

20. The product of claim 14 wherein:

half of the plurality of writing tracks are assigned for writing in the forward direction, with the other half assigned for writing in the reverse direction; and

the determination of the second writing track is further based, at least in part, on the assigned direction of the second track relative to a longitudinal direction of tape motion at a time when the flush indication data is received.