Applies to:

Abstract

This document will briefly discuss Multipath I/O and how Oracle Automatic Storage Management leverages multi-pathing.

History

Oracle ASM and Multi-Pathing Technologies

Nitin Vengurlekar

Jan 2010

Details

Full Document

For full article, download ASM multipathing (113K/pdf)

IMPORTANT: When using any multipath technology, ASM must be presented with Only One Path. ASM can not handle if more than one path for the same physical disk is presented to ASM.

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Summary

An I/O path generally consists of an initiator port, fabric port, target port, and LUN. Each permutation of this I/O path is considered an independent path. Dynamic Multi-pathing/failover tools aggregate these independent paths into a single logical path. This path virtualization provides I/O load-balancing across the HBAs, as well as non-disruptive failover on HBA failures. Multi-pathing software requires all the required disks to be visible on each available and eligible HBA. These multi-paths will be detected by probing the World Wide Device Identifiers (WWD ID).