Release Notes Device Mapper Multipath Enablement Kit for HP StorageWorks Disk Arrays v4.2.0 (AA-RWF9G-TE, March 2009)

Overview
This release notes discusses the recent product information about HP Device Mapper Multipath (HPDM
Multipath) Enablement Kit for HP StorageWorks Disk Arrays v4.2.0. This incremental release is to
provide enablement for HP StorageWorks Disk Arrays EVA6400/EVA8400.
Device Mapper Multipath offers the following features:
• 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.
• Path grouping policies: Paths are coalesced based on the following path-grouping policies:
1. Priority based path-grouping
• Provides priority to group paths based on Asymmetric Logical Unit Access (ALUA) state
• Provides static load balancing policy by assigning higher priority to the preferred path
2. Multibus
• All paths are grouped under a single path group
3. Group by serial
• Paths are grouped together based on controller serial number
4. Failover only
• Provides failover without load balancing by grouping the paths into individual path groups
• I/O load balancing policies: Provides weighted Round Robin load balancing policy within a path
group.
• Device name persistence: Device names are persistent across reboots and Storage Area Network
(SAN) reconfigurations. Device Mapper also provides configurable device name aliasing feature
for easier management.
• Persistent device settings: All the device settings such as load balancing policies, path grouping
policies are persistent across reboots and SAN reconfigurations.
• Device exclusion: Provides device exclusion feature through blacklisting of devices.
• Path monitoring: Periodically monitors each path for status and enables faster failover and failback.
• Online device addition and deletion: Devices can be added to or deleted from Device Mapper
(DM) multipath without rebooting the server or disrupting other devices or applications.
• Management Utility: Provides Command Line Interface (CLI) to manage multipath devices.
• Boot from SAN: Provides multipathing for operating system installation partitions on SAN device.
NOTE:
Multipathing for SAN Boot environment is supported on the following operating systems: RHEL 5
U2/RHEL 5 U3/SLES 10 SP2. For more details on multipathing support for SAN Boot environment,
see the Booting Linux x86 and x86_64 systems from a Storage Area Network with Device Mapper
Multipath document available at http://h18006.www1.hp.com/storage/networking/bootsan.html.
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