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For information about the layout of stripes and parity with each of these algorithms, see
RAID-5 Algorithms
(http://www.accs.com/p_and_p/RAID/LinuxRAID.html).
6.1.9 Multi-Disk Plug-In for EVMS
The Multi-Disk (MD) plug-in supports creating software RAIDs 0 (striping), 1 (mirror), 4 (striping
with dedicated parity), and 5 (striping with distributed parity). The MD plug-in to EVMS allows you
to manage all of these MD features as "regions" with the Regions Manager.
6.1.10 Device Mapper Plug-In for EVMS
The Device Mapper plug-in supports the following features in the EVMS MD Region Manager:
Multipath I/O: Connection fault tolerance and load balancing for connections between the
server and disks where multiple paths are available. If you plan to use multipathing, you should
configure MPIO for the devices that you plan to use in the RAID before configuring the RAID
itself. For information, see
IMPORTANT: The EVMS interface manages multipathing under the MD Region Manager,
which originally supported the
the interface and in naming of device nodes, but implements the storage objects with Device
Mapper.
Linear RAID: A linear concatenation of discontinuous areas of free space from the same or
multiple storage devices. Areas can be of different sizes.
Snapshots: Snapshots of a file system at a particular point in time, even while the system is
active, thereby allowing a consistent backup.
The Device Mapper driver is not started by default in the rescue system.
1 Open a terminal console, then log in as the
2 Start the Device Mapper by entering the following at the terminal console prompt:
/etc/init.d/boot.device-mapper start
6.2 Creating and Configuring a Software RAID
1 Open a terminal console, then log in as the
2 Start the EVMS GUI by entering the following at the terminal console prompt:
evmsgui
3 If the disks have not been initialized, initialize them by adding the DOS Segment Manager
now.
The following instructions assume you are initializing new disks. For information about
initializing an existing disk or a disk moved from another system, see
Disks," on page
36.
Repeat the following steps for each disk that you want to initialize:
3a Select Actions > Add > Segment Manager to Storage Object.
3b From the list, select the DOS Segment Manager, then click Next.
3c Select the device, then click Add to initialize it.
Chapter 5, "Managing Multipath I/O for Devices," on page
functions. It uses the legacy
md multipath
user or equivalent.
root
user or equivalent.
root
Linux
43.
terminology in
md
Section 4.2, "Initializing
Managing Software RAIDs with EVMS
81
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Troubleshooting
