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N-Times Read Performance Improvement on an N-Way Disk RAID Mirror

IP.com Disclosure Number: IPCOM000032239D
Publication Date: 2004-Oct-26
Document File: 2 page(s) / 229K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for an algorithm that improves the read-request file transfer of physical RAID mirrors. Benefits include improving performance up to the limit of the number of devices on the controller bus, and the maximum transfer rate of the bus.

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N-Times Read Performance Improvement on an N-Way Disk RAID Mirror

Disclosed is a method for an algorithm that improves the read-request file transfer of physical RAID mirrors. Benefits include improving performance up to the limit of the number of devices on the controller bus, and the maximum transfer rate of the bus.

Background

With typical RAID disk mirroring, a file read-request is sent to one of the disk members of the mirror, as determined by the hardware or software controller (see Figure 1). Currently, there are existing read-request performance improvements for reads in a mirror set; the read request may be submitted to all members of the mirror, and the file read is completed by the disk member that responds first. Other disk-selection algorithms (e.g. round-robin, current disk position, etc.) choose a mirror set member which is most likely to satisfy the read request first.

General Description

The disclosed method addresses a read request by interleaving it between all members of the mirror (see Figure 2). The entire read-request is not issued in parallel to all mirror members; rather, the read-request is separated into pieces which are divided between all mirror members. Each member provides a portion of the total request, and the controller composes the complete read-request. This results in the file-read request being completed by composing the results of the interleaved, divided requests at the controller level.

Note. The disclosed method only provides an impr...