Red Hat DEVICE-MAPPER MULTIPATH 5.2 Bedienungsanleitung PDF herunterladen (Seite 6)

DotHill – Linux Device Mapper Multipath “How To” for Storage Revision 4

• Alternate Paths: Redundant physical connectivity between a host system equipped with

multiple HBAs and the SANnet storage array

• Failover: Constantly monitors each path and automatically reroutes I/O operations over a

functioning alternate path upon the failure of a path

• Failback: Optionally moves the I/O operations back to a path that had failed but has been

repaired

• Transparency: Implements failover or failback transparently without disrupting higher-level

applications

• Monitoring: Notifies the user if there is a change in the path status

• Load Balancing: Distributes the I/O operations among all available paths to enhance

performance

• Flexible Management: Uses a CLI with a rich choice of display options to configure and

manage multipath features

• User-Friendly Names: Provides an option for customized names of the DM-MP devices

• Naming Persistence: Names of DM-MP devices persist across reboots even if there are

changes in the attached storage configuration

This first release of Device Mapper is intended for use in test environments and for applications

that are not mission-critical.

3.2 Software components of DM-MP

There are four software components of DM-MP:

dm-multipath kernel module - This module routes I/O among paths and path groups.

multipath configuration tool - This command configures, lists, and removes multipath devices.

The command is run in rc.sysinit during startup and by udev whenever a new block device is

added. It can also be used to interactively modify the attributes of multipath devices.

multipath daemon - This daemon monitors paths by checking to see if faulty paths have been

repaired. When paths come back to life, the multipath daemon may also initiate changes to

ensure that the optimal path group is being used.

kpartx utility - This utility creates DM-MP devices for partitions on a device. You must use this

command for MS-DOS based partitions.

4 Theory of Operation

When there are multiple paths to a storage array each path appears as a separate block device.

This results in multiple block devices that refer to the same storage resource or logical unit (LU).

For example, if a single LU is presented through two ports in a storage array which is connected

to a host with two HBAs through a single unzoned Fibre Channel switch, the host will see four

1 2 3 4 5 6 7 8 9 10 11 ... 29 30

Keine Kommentare

Red Hat DEVICE-MAPPER MULTIPATH 5.2 Bedienungsanleitung Seite 6