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METHOD AND MEANS FOR ENHANCED DATA SCRUBBING OF RAID 0, AND 5 ARRAYS

IP.com Disclosure Number: IPCOM000013499D
Original Publication Date: 2000-Mar-01
Included in the Prior Art Database: 2003-Jun-18

Publishing Venue

IBM

Abstract

Disclosed is an algorithm and implementation in a Redundant Array Inexpensive Disk (RAID) controller's firmware to detect the growth of medium defects and to reconstruct the affected area in the array efficiently. The process of detecting and reconstructing is referred to as Data Scrubbing in this disclosure. In a RAID technology, multiple physical drives are bundled together to form what is referred to as an array. An array is configured into various RAID levels to enhance either performance or fault tolerance. The data are striped across all the physical drives which make up the logical drive. Therefore, when a medium defect grows on one of the physical drives, data availability is affected for the stripe unit spanning the medium defect for RAID 0. However, data availability is maintained for RAID 1, which mirrors its disk, and RAID 5, which reconstructs the data from its parity. The Data Scrubbing detects a grown defect and fixes it in the background automatically and efficiently. In addition, the entire logical drive must be "scrubbed" within a reasonable time period at maximum system load. Data scrubbing time insures defect detection and correction when system operates at its peak for long periods of time. Having a minimum scrubbing time prevents over taxing the drives causing premature wear.