Browse Prior Art Database

Raid Disk Arrays with Redundant Configuration Data

IP.com Disclosure Number: IPCOM000117420D
Original Publication Date: 1996-Feb-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 96K

Publishing Venue

IBM

Related People

Iwata, K: AUTHOR [+3]

Abstract

Disclosed is Redundant Arrays of Independent Disks (RAID) which have redundant configuration data. With this method the disk arrays can operate with an original configuration even if the controller card is replaced. Thus, it prevents from undesirable data loss or complicated restoration procedure.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Raid Disk Arrays with Redundant Configuration Data

      Disclosed is Redundant Arrays of Independent Disks (RAID) which
have redundant configuration data.  With this method the disk arrays
can operate with an original configuration even if the controller
card is replaced.  Thus, it prevents from undesirable data loss or
complicated restoration procedure.

      In most implementations of RAID disk arrays, a non volatile
RAM on the RAID controller card contains configuration data, which
includes the number of used drives, RAID level, existence of hot
spare drives and all other information necessary to operate RAID
disk array.  The RAID controller interprets command issued by host
computer and process that command by means of issuing command to
physical HDD's with physical LBA.  This interpretation is based on
the configuration data.  Thus, the loss of configuration data means
the loss of data for users.  With the traditional method, the
configuration data only lies in the non volatile RAM on the RAID
controller card.  If the controller card fails and needs to be
replaced, a complicated recovery procedure is necessary to restore
the configuration data before replacement.

      The Figure shows a block diagram of RAID disk arrays disclosed
in this article.  Though the Figure shows only four hard disks, the
invention does not depend on the number of them.  The RAID disk array
consists of RAID controller (2), Power supply (17) and hard disk-1
(8) through hard disk-4 (11).  The RAID controller (2) and hard disk
drives (8)-11) are connected by drive interface (16).  RAID disk
array itself is connected to a host computer through host interface
(1).  RAID controller (2) consists of control circuit (3), CPU (4),
RAM (5) and non volatile RAM (6).  The control circuit (3) is
controlled by firmware which runs on the CPU (4).  A command received
from host computer through the host interface (1) is interpreted by
the firmware and executed by means of controlling hard disk drives
(8)-(11) through the control circuit (3).  A configuration data (7)
is stored in the non volatile RAM (6) on the control circuit (3).
The firmware converts logical address in the command from host
computer into physical address (number of...