Method and apparatus for optimizing prefetch caching by reverse ordering of logical blocks

Claim 1

A method of arranging logical data blocks in physical block locations in a disc drive type storage unit having a plurality of discs, each of said discs having a top and bottom surface, each of said disc surfaces having a plurality of bands, each band having a plurality of tracks and each track having a plurality of sectors, and each said disc drive having a plurality of heads, each head associated with a top or bottom surface of one of said plurality of discs, and each of said tracks on each of said surfaces associated with each of said heads forming a cylinder, said method comprising the steps of: determining parameters of said disc storage unit, said parameters comprising at least the number and order of said sectors in each of said tracks for each of said cylinders in said disc drive and the number and order of said tracks in each of said cylinders; and assigning logical block numbers to said disc drive in the reverse order of said tracks and sectors in said cylinders so that said logical block numbers for said top and bottom surfaces of each of said discs pass under said associated head in decreasing order from one of said heads to the next.

Claim 2

A method of arranging logical data blocks in physical block locations in a disc drive type storage unit having a plurality of discs, each of said discs having a top and bottom surface, each of said disc surfaces having a plurality of bands, each band having a plurality of tracks and each track having a plurality of sectors, and each said disc drive having a plurality of heads, each head associated with a top or bottom surface of one of said plurality of discs, and each of said tracks on each of said surfaces associated with each of said heads forming a cylinder, said method comprising the steps of: determining parameters of said disc storage unit, said parameters comprising at least the number and order of said sectors in each of said tracks for each of said cylinders in said disc drive and the number and order of said tracks in each of said cylinders; and assigning logical block numbers to said disc drive in the reverse order of said tracks and sectors in said cylinders so that said logical block numbers for said top and bottom surfaces of each of said discs pass under said associated head in decreasing order from one of said heads to the next.

Claim 3

A method of arranging logical data blocks in physical block locations in a plurality of disc drive type storage units, each of said disc drive type storage units having a plurality of bands, each of said discs having a top and bottom surface, each of said disc surfaces having a plurality of bands, each band having a plurality of tracks and each track having a plurality of sectors, and each said disc drive having a plurality of heads, each head associated with a top or bottom surface of one of said plurality of discs, and each of said tracks on each of said surfaces associated with each of said heads forming a cylinder, said method comprising the steps of: determining parameters of each said disc drive storage unit said parameters comprising at least the number and order of said sectors in each of said tracks for each of said cylinders in each said disc drive and the number and order of said tracks in each of said cylinders; and assigning logical block numbers to each said disc drive in the reverse order of said tracks and sectors in said cylinders so that said logical block numbers for said top and bottom surfaces of each of said discs pass under said associated head in decreasing order from one of said heads to the next.

Claim 4

A method of arranging logical data blocks in physical block locations in a plurality of disc drive type storage units, each of said disc drive type storage units having a plurality of bands, each of said discs having a top and bottom surface, each of said disc surfaces having a plurality of bands, each band having a plurality of tracks and each track having a plurality of sectors, and each said disc drive having a plurality of heads, each head associated with a top or bottom surface of one of said plurality of discs, and each of said tracks on each of said surfaces associated with each of said heads forming a cylinder, said method comprising the steps of: determining parameters of each said disc drive storage unit said parameters comprising at least the number and order of said sectors in each of said tracks for each of said cylinders in each said disc drive and the number and order of said tracks in each of said cylinders; and assigning logical block numbers to each said disc drive in the reverse order of said tracks and sectors in said cylinders so that said logical block numbers for said top and bottom surfaces of each of said discs pass under said associated head in decreasing order from one of said heads to the next.

Claim 12

A method of arranging logical data blocks in physical block locations in a set of disc drive type storage units, each disc drive having a plurality of discs, each of said discs having a top and bottom surface, each of said disc surfaces having a plurality of bands, each band having a plurality of tracks and each track having a plurality of sectors, and each said disc drive having a plurality of heads, each head associated with a top or bottom surface of one of said plurality of discs, and each of said tracks on each of said surfaces associated with each of said heads forming a cylinder, said method comprising the steps of: determining parameters of said disc drive storage units, said parameters comprising the number and order of said disc drives, the number and order of said bands on each of said disc drives, the number and order of said cylinders for each of said bands, the number and order of said sectors in each of said tracks for each of said bands and the number and order of said tracks in each of said cylinders; and assigning logical block numbers to all of said disc drives in the reverse order of said disc drives, bands, cylinders, tracks and sectors so that said logical block numbers for said top and bottom surfaces of each of said discs pass under said associated head in decreasing order from one of said heads to the next.

Claim 13

A method of arranging logical data blocks in physical block locations in a set of disc drive type storage units, each disc drive having a plurality of discs, each of said discs having a top and bottom surface, each of said disc surfaces having a plurality of bands, each band having a plurality of tracks and each track having a plurality of sectors, and each said disc drive having a plurality of heads, each head associated with a top or bottom surface of one of said plurality of discs, and each of said tracks on each of said surfaces associated with each of said heads forming a cylinder, said method comprising the steps of: determining parameters of said disc drive storage units, said parameters comprising the number and order of said disc drives, the number and order of said bands on each of said disc drives, the number and order of said cylinders for each of said bands, the number and order of said sectors in each of said tracks for each of said bands and the number and order of said tracks in each of said cylinders; and assigning logical block numbers to all of said disc drives in the reverse order of said disc drives, bands, cylinders, tracks and sectors so that said logical block numbers for said top and bottom surfaces of each of said discs pass under said associated head in decreasing order from one of said heads to the next.

Claim 18

A method of arranging logical data blocks in physical block locations in a striped set of disc drive type storage units so that all of said disc drives are presented as a single logical volume for input/output requests, said logical data blocks are arranged into chunks, each of said disc drives having a plurality of discs, each of said discs having a top and bottom surface, each of said disc surfaces having a plurality of bands, each band having a plurality of tracks and each track having a plurality of sectors, and each said disc drive having a plurality of heads, each head associated with a top or bottom surface of one of said plurality of discs, and each of said tracks on each of said surfaces associated with each of said heads, forming a cylinder, said method comprising the steps of: determining parameters of said disc drive storage units, said parameters comprising the number and order of said disc drives, the number and order of said hands on each of said disc drives, the number and order of said cylinders for each of said bands, the number and order of said tracks for each of said cylinders, the number and order of said sectors for each of said tracks in each of said bands and the number of said tracks for each stripe; assigning a full stripe boundary to each of said bands in each of said disc drives by determining the number of chunks defined in logical data blocks that are evenly divisible into the number of logical blocks in each of said bands; assigning a short stripe boundary as the portion of each of said bands remaining after said full stripe boundary, when said chunk defined in logical blocks does not evenly divide into the number of logic blocks in each said band; and assigning logical block numbers to all of said disc drives in the reverse order of said sectors and tracks in said assigned strips in said striped set of disc drives from the top track of the outermost of said cylinders of the innermost of said bands to the bottom track of the innermost of said cylinders of the outermost of said bands with a sector offset between said tracks in each of said cylinders, said sector offset corresponding to the number of said sectors passed during a head switch operation between said tracks in each of said cylinders.

Claim 19

A method of arranging logical data blocks in physical block locations in a striped set of disc drive type storage units so that all of said disc drives are presented as a single logical volume for input/output requests, said logical data blocks are arranged into chunks, each of said disc drives having a plurality of discs, each of said discs having a top and bottom surface, each of said disc surfaces having a plurality of bands, each band having a plurality of tracks and each track having a plurality of sectors, and each said disc drive having a plurality of heads, each head associated with a top or bottom surface of one of said plurality of discs, and each of said tracks on each of said surfaces associated with each of said heads, forming a cylinder, said method comprising the steps of: determining parameters of said disc drive storage units, said parameters comprising the number and order of said disc drives, the number and order of said hands on each of said disc drives, the number and order of said cylinders for each of said bands, the number and order of said tracks for each of said cylinders, the number and order of said sectors for each of said tracks in each of said bands and the number of said tracks for each stripe; assigning a full stripe boundary to each of said bands in each of said disc drives by determining the number of chunks defined in logical data blocks that are evenly divisible into the number of logical blocks in each of said bands; assigning a short stripe boundary as the portion of each of said bands remaining after said full stripe boundary, when said chunk defined in logical blocks does not evenly divide into the number of logic blocks in each said band; and assigning logical block numbers to all of said disc drives in the reverse order of said sectors and tracks in said assigned strips in said striped set of disc drives from the top track of the outermost of said cylinders of the innermost of said bands to the bottom track of the innermost of said cylinders of the outermost of said bands with a sector offset between said tracks in each of said cylinders, said sector offset corresponding to the number of said sectors passed during a head switch operation between said tracks in each of said cylinders.