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SUSE Linux Enterprise Server (SLES 10) Installation and Administration
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10.4 Using the Devices

MPIO devices can be used directly, with LVM, and with mdadm.

10.4.1 Using the Devices Directly

If you want to use the entire LUNs directly (for example, if you are using the SAN features to partition your storage), you can simply use the /dev/disk/by-name/xxx names directly for mkfs, fstab, your application, etc.

10.4.2 Using LVM2

To make LVM2 recognize the MPIO devices as possible physical volumes, you must modify /etc/lvm/lvm.conf. It is important to modify it in a way that it does not scan and use the physical paths, but only accesses the multipath IO storage through the multipath IO layer. To do so, change the filter and types entry in /etc/lvm/lvm.conf as follows:

filter = [ "a|/dev/disk/by-name/.*|", "r|.*|" ]
types = [ "device-mapper", 253 ]

This allows LVM2 to scan only the by-name paths and reject everything else. If you are also using LVM2 on non-multipath IO devices, make the necessary adjustments to suit your setup.

10.4.3 Using mdadm

The same as for LVM2 applies to mdadm as well—the devices must be accessed by name rather than by physical path. Therefore the DEVICE entry in /etc/mdadm.conf must be modified:

DEVICE /dev/disk/by-name/*

10.4.4 Partitions

Currently it is not possible to partition multipath IO devices themselves. If the underlying physical device is already partitioned, the multipath IO device reflects those partitions and the layer provides /dev/disk/by-name/>name<p1 ... pN devices so you can access the partitions through the multipath IO layer.

As a consequence, the devices need to be partitioned prior to enabling multipath IO. If you change the partitioning in the running system, Multipath IO does not automatically detect and reflect these changes. It must be reinitialized, which usually requires a reboot.

SUSE Linux Enterprise Server (SLES 10) Installation and Administration
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  Published Courtesy of Novell, Inc. Design by Interspire