Data correcting applicable to redundant arrays of independent disks

• US 5,233,618 A
• Filed: 03/02/1990
• Issued: 08/03/1993
• Est. Priority Date: 03/02/1990
• Status: Expired due to Term

• Current Assignee: EMC Corporation (Dell Technologies Inc.)
• Original Assignee: Micron Technology, Inc.
• Inventors: Glider, Joseph S., Idleman, Thomas E., Powers, David T.
• Primary Examiner(s): Baker, Stephen M.
• Application Number:
  US07/488,750
• Time in Patent Office: 1,250 Days
• Field of Search: 371/51.1, 371/21.2, 371/68.1, 371/40.1
• US Class Current: 714/6.12
• CPC Class Codes: G06F 11/08 Error detection or correction by redundancy in data representation, e.g. by using checking codes
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 11/1612 where the redundant component is persistent storage
• CPC Class Codes: G06F 2211/1007 Addressing errors, i.e. silent errors in RAID, e.g. sector slipping and addressing errors
• CPC Class Codes: G06F 2211/104 Metadata, i.e. metadata associated with RAID systems with parity
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0673 Single storage device
• CPC Class Codes: G11C 29/70 Masking faults in memories by using spares or by reconfiguring
• CPC Class Codes: G11C 29/88 with partially good memories

Abstract

Methods and apparatus are provided for detecting and correcting various data errors that may arise in a mass data storage apparatus comprising a set of physical mass storage devices operating as one or more larger logical mass storage devices. A method and apparatus is provided for detecting and reconstructing incorrectly routed data. A method and apparatus is also provided for detecting when one or more physical devices fails to write a block of data, and for reconstructing lost data.

Claims

1. A mass data storage apparatus comprising:

a set of physical mass storage devices operatively interconnected so as to function as at least one logical mass storage device;

means for reading blocks of data from and writing blocks of data to the set of physical mass storage devices; and

means for validating blocks of data read from or written to the set of physical mass storage devices, wherein the validating means comprises mean for performing the following functions;

(a) when writing a block of data to a device of the set, storing with the block of data on the device, information identifying the intended logical storage location for the block of data, and, when reading a block of data from a device of the set, detecting whether the block of data that is read was misdirected within the apparatus when written by comparing the identifying information stored with the read block of data and a logical address associated with the logical storage location form which the block of data is read; and

(b) when writing a block of data to a device of the set, storing with the block of data on the device, information identifying the write operation by which the block of data is written and storing with a selected block of data on another device of the set, information identifying the same write operation, and, when reading the block of data, detecting whether the identified write operation was completed by comparing the identifying information stored with the read block of data to the identifying information stored with the selected block of data on another device.

2. In a mass data storage apparatus comprising a set of physical mass storage devices at least a plural number of which are operatively interconnected so as to function as a single logical data storage unit, the logical unit being operable in a transaction mode wherein data blocks stored in the logical unit may be individually modified, a method for detecting whether a write operation intended to modify a data block within the logical unit was completed, the method comprising:

arranging the devices of the logical unit intended to store data blocks into groups such that the devices of each group are read and written in parallel;

when modifying a data block on one device, storing a time stamp on the one device and other devices in the group indicating when the block of data was modified; and

comparing the time stamp stored on the one device to the time stamps stored on the other devices of the group to determine if the time stamps correspond to one another.

3. A mass data storage apparatus comprising:

a set of physical mass storage devices operatively interconnected so as to function as at least one logical mass storage device;

means for reading blocks of data from and writing blocks of data to the set of physical mass storage devices; and

means for validating blocks of data read from or written to the set of physical mass storage devices, wherein the validating means comprises means for, when writing a block of data to a device of the set, storing with the block of data on the device information identifying the write operation by which the block of data is written and storing with a selected block of data on another device of the set information identifying the same write operation, and, when reading the block of data, detecting whether the identified write operation was completed by comparing the identifying information stored with the read block of data to the identifying information stored with the selected block of data on another device.