Raid-5 parity generation and data reconstruction

• US 5,805,788 A
• Filed: 05/20/1996
• Issued: 09/08/1998
• Est. Priority Date: 05/20/1996
• Status: Expired due to Term

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: CRAY Incorporated (Hewlett-Packard Enterprise Company)
• Inventors: Johnson, Timothy J.
• Primary Examiner(s): Beausoliel, Jr., Robert W.
• Assistant Examiner(s): Le, Dieu-Minh
• Application Number:
  US08/650,336
• Time in Patent Office: 841 Days
• Field of Search: 395/182.04, 395/182.03, 395/182.18, 395/441, 371/49.1, 371/49.2, 371/2.2, 371/21.1, 371/40.1, 371/50.1
• US Class Current: 714/6.12
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 2211/1059 Parity-single bit-RAID5, i.e. RAID 5 implementations

Abstract

A system for implementing RAID-5 parity generation and reconstruction. Data for an array of disk drives is placed in an I/O buffer. The RAID-5 parity engine creates parity data and stores the resulting parity data in the I/O buffer as well. The I/O buffer (both the data and the parity) is then sector-striped across a network of disk drives, such as a Fibre Channel network. The RAID-5 parity engine creates parity on multiple stripes of data upon a single activation of the engine. The RAID-5 parity engine can reconstruct a sector of data using the parity information. The RAID-5 parity engine can also check the data against its expected parity.

Claims

1. In a computer system having a plurality of disk drives connected over a time multiplexed network, a method for storing data, comprising the steps of:

providing a channel interface;

connecting the channel interface to an I/O buffer memory and to the plurality of disk drives over the time multiplexed network;

calculating a sector size;

calculating a stripe width;

calculating a stripe count;

reading stored striped data sectors from the I/O buffer memory, wherein the size of each striped data sector is a function of said sector size, said stripe width and said stripe count;

generating parity sectors from the striped data sectors read from the I/O buffer memory, wherein the size of each parity sector is a function of said sector size, said stripe width and said stripe count;

storing the parity sectors to the I/O buffer memory; and

writing the stored striped data sectors and parity sectors from the I/O buffer memory through the channel interface to the plurality of disk drives.

2. The method for storing data as recited in claim 1, wherein the step of generating parity data comprises:

generating parity for the identified stripe width and sector size; and

repeating the generation of parity for the identified stripe count.

3. The method for storing data as recited in claim 1, wherein the step of generating parity data further comprises the steps of:

generating initial parity from striped data;

generating validity parity to compare stored parity with anticipated parity;

generating reconstruction parity to repair corrupted data; and

storing the reconstructed parity sectors to the I/O buffer memory; and

wherein the channel controller transfers reconstructed parity sectors in the I/O buffer memory to the plurality of disk drive devices.

4. A RAID-5 system, comprising:

an I/O interface system; and

a plurality of disk drive devices connected over a time multiplexed network to said I/O interface system;

wherein, the I/O interface system comprises;

a channel interface;

an I/O buffer memory holding striped data sectors, wherein the size of each striped data sector is a function of said sector size, said stripe width and said stripe count;

a RAID-5 parity generator connected to the I/O buffer memory, wherein the RAID-5 parity generator reads striped data sectors stored in the I/O buffer memory calculates parity sectors as a function of the data sectors read from the I/O buffer memory and saves said parity sectors calculated by said parity generator to the I/O buffer memory, wherein the size of each parity sector is a function of said sector size, said stripe width and said stripe count; and

a channel controller which transfers striped data sectors and parity sectors stored in the I/O buffer memory to the plurality of disk drive devices.

5. The RAID-5 system, as recited in claim 4, wherein the I/O interface system further comprises,

a sector size indicator;

a stripe width indicator;

a stripe count indicator; and

wherein the RAID-5 parity generator calculates parity sectors using the sector size indicator and stripe width indicator and repeats the calculating of parity sectors based on the stripe count indicator.

6. The RAID-5 system, as recited in claim 4, wherein the RAID-5 parity generator also generates validity parity to check stored parity and reconstructs parity sectors and stores reconstructed parity sectors to the I/O buffer memory;

and

wherein the channel controller transfers reconstructed parity sectors in the I/O buffer memory to the plurality of disk drive devices.