Browse Prior Art Database

Pacing a Redundant Arrays Independent Disks Sparing Operation

IP.com Disclosure Number: IPCOM000116655D
Original Publication Date: 1995-Oct-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Hyde, J: AUTHOR [+4]

Abstract

A method for minimizing Head-Disk-Assembly (HDA) arm movement when sparing a RAID drawer containing two Logical Volumes is disclosed. The method will also insure that there are at least two paths from the control unit to the drawer available for customer activity.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Pacing a Redundant Arrays Independent Disks Sparing Operation

      A method for minimizing Head-Disk-Assembly (HDA) arm movement
when sparing a RAID drawer containing two Logical Volumes is
disclosed.  The method will also insure that there are at least two
paths from the control unit to the drawer available for customer
activity.

      When a single error occurs in a drawer, the attached control
unit will initiate a sparing operation by starting a Dual Copy
Establish operation for each logical volume.

      A Sparing Control Area will be initialized for each copy
operation to indicate that the copy has started and has a current
cylinder value of 0.  The Dual Copy Establish overlaps the staging
and destaging operations and the Sparing Control Areas will be used
to synchronize the two copy operations and limit the control unit
paths used at any point in time.

      A stage of Cylinder 0 of Logical Volume 0 is initiated.  The
drawer will stage all tracks on the cylinder from the HDAs into the
drawer cache and while the tracks are being read into the control
unit cache, data from the HDAs continues to be read into data buffers
associated with each HDA.  When the cylinder has been staged, destage
operations are scheduled to destage the cylinder to the spare drawer.
The cylinder value in the Sparing Control Area for Volume 0 is
incremented to 1.
  Table 1 (Page 1 of 2). Raid mapping for 2 logical volumes in a 4
                         HDA drawer
  logical Volume & Cylinder    HDA 0      HDA 1       HDA 2      HDA
3
  Logical Volume 0 -           track 0    track 1     track 2
parity
  Cylinder 0
                               track 3    track 4     track 5
parity
                               track 6    track 7     track 8
parity
                               track 9    track A     track B
parity
                               track C    track D     track E
parity
  Logical Volume 1 -           track 0    track 1     track 2
pa...