Cache management for data transfer control from target disk areas

A cache manager for managing data transfer between a disk drive and a cache buffer including a plurality of data blocks for storing data, the data disk drive including a data disk with a plurality of concentric data tracks thereon, a spindle motor for rotating the data disk, and a transducer supported by a carrier for moving the transducer radially across the data disk to write data to or read data from the data tracks, the cache manager comprising a logic circuit interconnected to the disk drive and to the cache buffer, wherein the logic circuit is configured by program instructions such that in response to a request for retrieving a set of data blocks from the data disk, the logic circuit performs steps including:

• (a) selecting a track on the data disk where said set of data blocks reside;
• (b) defining a data segment on the selected track, wherein the data segment comprises, in sequence:
• (1) a pre-fetch data area, (2) a fetch data area comprising said set of data blocks, and (3) a post-fetch data area;
• (c) directing the carrier to position the transducer over the selected track;
• (d) determining a landing position of the transducer over the selected track relative to the data segment;
• and
• (e) controlling transfer of data from the data segment to the cache buffer based on said landing position, wherein:
• (1) if said landing position is outside the data segment, delaying reading data from the data segment until the pre-fetch data area rotates under the transducer, thereafter commencing reading data from the pre-fetch area;
• (2) otherwise, commencing reading data from said landing position in the data segment without delay.

In a cache system comprising a cache buffer including a plurality of data blocks for storing data, and a cache manager for transferring data into and out of the cache buffer, including retrieving data from a disk drive and storing said data into the cache buffer, the disk drive comprising a data disk having a plurality of concentric data tracks thereon, a spindle motor for rotating the data disk, and a transducer supported by a carrier for positioning the transducer over a selected data track to write data thereto or read data therefrom,

• a method of data transfer in response to a request for retrieving a set of data blocks from the selected track, comprising the steps of:
• (a) defining a data segment comprising, in sequence:
• (1) a pre-fetch data area spanning at least a portion of at least one preceding track to the selected track and at least a portion of the selected track, (2) a fetch data area comprising said set of data blocks on the selected track, and (3) a post-fetch data area on the selected track;
• (b) determining a landing position of the transducer over the selected track relative to the data segment;
• and
• (c) controlling transfer of data from the data segment to the cache buffer based on said landing position, wherein:
• (1) if said landing position is inside the data segment, commencing reading data from said landing position in the data segment without delay;
• and
• (2) otherwise, if said landing position is outside the data segment:
• (i) positioning the transducer over said preceding track, (ii) determining the position of the transducer over the preceding track relative to the data segment, (iii) if the transducer position is within the pre-fetch area, commencing reading data from said transducer position in the pre-fetch area without delay, otherwise, (iv) delaying reading data from the data segment until the pre-fetch data area rotates under the transducer, thereafter commencing reading data from the pre-fetch area.

A cache manager for managing data transfer between a disk drive and a cache buffer including a plurality of data blocks for storing data, the data disk drive including a data disk with a plurality of concentric data tracks thereon, a spindle motor for rotating the data disk, and a transducer supported by a carrier for moving the transducer radially across the data disk to write data to or read data from the data tracks, the cache manager comprising a logic circuit interconnected to the disk drive and to the cache buffer, wherein the logic circuit is configured by program instructions such that in response to a request for retrieving a set of data blocks from the data disk, the logic circuit performs steps including:

• (a) selecting a track on the data disk where said set of data blocks reside;
• (b) defining a data segment comprising, in sequence:
• (1) a pre-fetch data area spanning at least a portion of at least one preceding track to the selected track and at least a portion of the selected track, (2) a fetch data area comprising said set of data blocks on the selected track, and (3) a post-fetch data area on the selected track;
• (c) directing the carrier to position the transducer over the selected track;
• (d) determining a landing position of the transducer over the selected track relative to the data segment;
• and
• (e) controlling transfer of data from the data segment to the cache buffer based on said landing position, wherein:
• (1) if said landing position is inside the data segment, commencing reading data from said landing position in the data segment without delay;
• and
• (2) otherwise, if said landing position is outside the data segment:
• (i) positioning the transducer over said preceding track, (ii) determining the position of the transducer over the preceding track relative to the data segment, (iii) if the transducer position is within the pre-fetch area, commencing reading data from said transducer position in the pre-fetch area without delay, otherwise, (iv) delaying reading data from the data segment until the pre-fetch data area rotates under the transducer, thereafter commencing reading data from the pre-fetch area.

In a cache system comprising a cache buffer including a plurality of data blocks for storing data, and a cache manager for transferring data into and out of the cache buffer, including retrieving data from a disk drive and storing said data into the cache buffer, the disk drive comprising a data disk having a plurality of concentric data tracks thereon, a spindle motor for rotating the data disk, and a transducer supported by a carrier for positioning the transducer over a selected data track to write data thereto or read data therefrom,

• a method of data transfer in response to a request for retrieving a set of data blocks from the selected track, comprising the steps of:
• (a) defining a data segment comprising, in sequence:
• (1) a pre-fetch data area on the selected track, (2) a fetch data area comprising said set of data blocks on the selected track, and (3) a post-fetch data area spanning at least a portion of the selected track and at least a portion of at least one succeeding track to the selected track, wherein the post-fetch area includes a first segment in said portion of the selected track and a second segment in said potion of said succeeding track;
• and
• (b) determining a landing position of the transducer over the selected track relative to the data segment;
• and
• (c) controlling transfer of data from the data segment to the cache buffer based on said landing position, wherein:
• (1) if said landing position is inside the data segment, commencing reading data from said landing position in the data segment without delay;
• and
• (2) otherwise, if said landing position is outside the data segment:
• (i) positioning the transducer over said succeeding track, (ii) determining the position of the transducer over said succeeding track relative to the data segment, (iii) if the transducer position is within the post-fetch area, commencing reading data from said transducer position in the post-fetch area without delay, otherwise, (iv) delaying reading data from the data segment until the post-fetch data area rotates under the transducer, thereafter commencing reading data from the post-fetch area.

A cache manager for managing data transfer between a disk drive and a cache buffer including a plurality of data blocks for storing data, the data disk drive including a data disk with a plurality of concentric data tracks thereon, a spindle motor for rotating the data disk, and a transducer supported by a carrier for moving the transducer radially across the data disk to write data to or read data from the data tracks, the cache manager comprising a logic circuit interconnected to the disk drive and to the cache buffer, wherein the logic circuit is configured by program instructions such that in response to a request for retrieving a set of data blocks from the data disk, the logic circuit performs steps including:

• (a) selecting a track on the data disk where said set of data blocks reside;
• (b) defining a data segment comprising, in sequence:
• (1) a pre-fetch data area on the selected track, (2) a fetch data area comprising said set of data blocks on the selected track, and (3) a post-fetch data area spanning at least a portion of the selected track and at least a portion of at least one succeeding track to the selected track;
• (c) directing the carrier to position the transducer over the selected track;
• (d) determining a landing position of the transducer over the selected track relative to the data segment;
• and
• (e) controlling transfer of data from the data segment to the cache buffer based on said landing position, wherein:
• (1) if said landing position is inside the data segment, commencing reading data from said landing position in the data segment without delay;
• and
• (2) otherwise, if said landing position is outside the data segment:
• (i) positioning the transducer over said succeeding track, (ii) determining the position of the transducer over said succeeding track relative to the data segment, (iii) if the transducer position is within the post-fetch area, commencing reading data from said transducer position in the post-fetch area without delay, otherwise, (iv) delaying reading data from the data segment until the post-fetch data area rotates under the transducer, thereafter commencing reading data from the post-fetch area.