Application Notes Device Mapper Multipath with Oracle ASM on Linux (5697-7806, April 2009)

Document overview
This document focuses on the best practices to leverage the features provided by Device Mapper
Multipath wh
ile deploying Oracle Automatic Storage Management (AS M) on Linux.
This document is not designed to replace the documentation supplied with individual solution components.
It is intended to provide customers an additional resource for configuring Oracle ASM with Device
Mapper multipath on Linux.
Intended audience
This document is intended for users who would be deploying Oracle ASM with Device M apper Multipath
on Linux operating systems.
Prerequisites
This docum
ent assumes that the user is familiar with the following c oncepts:
• Oracle AS M
• Linux Device Mapper Multipath
Information not provided
This d ocument does not provide the following information:
• Installation and array specificconfiguration settings for D evice M apper multipath
• Installation and configuration of Oracle database
Introduction
Automatic Storage Management (ASM) is a feature of Oracle 10g database that provides the services of
a filesystem, logical volume manager, and software RAID in a platform -independent manner.
From a hardware configuration standpoint, high availability means eliminating single points of failure
which is a key requirement. Multipathing is an imp ortant aspect of high availability con fi gurations. HP
recomme
nds Device M apper Multipath as multipathing solution on Linux.
This d ocument assumes that the storage devices used by Oracle ASM are the logical d rives or LUs
with multiple pa ths.
Device Mapper Multipath for Linux
Device Mapper (DM) is an infrastructure included in the Linux kernel, which provides a generic way
to create virtual layers of block devices. The multipathing feature is provided with the combination
of DM Multipath kernel modules and multipath-tools userspace package. DM Multipath provides the
following key benefits:
• I/O failover and failback: Provides transparent failover and failback of I/Os by rerouting I/Os
automatically to an alternative path when a path failure is sensed and routing them back when
the path is restored.
• I/O load balancing policies: Provides weighted Round Robin load balancing policy within a p ath
group.
• Device name p ersi stence : Device names are persistent acr oss reboots and Stor age Area Network
(SAN) reconfigurations. Device Mapper also provides configurabledevicenamealiasingfeaturefor
easier management.
• Persistent device setting s: All the device settings such as load balancing policies, path grouping
policies are persistent across reboots and SA N reconfigurations.
• Path monitoring: Periodically m onitors each path for status and enables faster failover and failback.
Device Mapper Multipath with Oracle ASM on Linux
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