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Improvement of Mirrored Drive Performance - Offset Mirrored Striping

IP.com Disclosure Number: IPCOM000123798D
Original Publication Date: 1999-May-01
Included in the Prior Art Database: 2005-Apr-05
Document File: 4 page(s) / 86K

Publishing Venue

IBM

Related People

Takada, H: AUTHOR

Abstract

Disclosed is a method of data mapping on mirroring disks or, RAID (Redundant Array of Independent Disks) LEVEL 1, to improve sequential read performance. By the conventional data mapping on mirrored drives, the sequential read performance hardly exceeds a single hard disk drive (HDD). With this method, the sequential read performance can exceed a single HDD without any additional hardware to mirrored drives (hardware mirror and software mirror). This realizes low cost, high reliability, high performance mirrored disks or disk array, oriented to sequential read.

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Improvement of Mirrored Drive Performance - Offset Mirrored Striping

   Disclosed is a method of data mapping on mirroring disks
or, RAID (Redundant Array of Independent Disks) LEVEL 1, to improve
sequential read performance.  By the conventional data mapping on
mirrored drives, the sequential read performance hardly exceeds a
single hard disk drive (HDD).  With this method, the sequential read
performance can exceed a single HDD without any additional hardware
to mirrored drives (hardware mirror and software mirror).  This
realizes low cost, high reliability, high performance mirrored disks
or disk array, oriented to sequential read.

   In mirrored drives, same data is written on a couple of
hard disk drives (HDD)( Figure 1 ).
  While in striping mode (RAID LEVEL 0), data is distributed onto all
drives (Figure 2).

   Since the data mapping pattern in RAID 1 (Figure 1) is
similar to single HDD, sequential read performance is not greater
than single HDD.  While in RAID 0 (Figure 2), both HDD's has
different stripes of data therefore, both HDD's can be accessed
simultaneously for sequential read and performance is greater than
single HDD.

   In the offset mirrored striping mode (this method), data
map ping is as shown in Figure 3.

   From DATA 1 through DATA 8 are mapped in the same manner
as RAID 0 (striping mode), except followed by offset mirrored data.
In sequential read access to DATA 1 through DATA 8, data transfer
rate can be improved up to twice of a sin...