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PowerPath for UNIX Installation and Administration Guide
PowerPath Administration on Solaris
Pseudo Devices
A pseudo device describes a device special file of one of the following
forms:
◆ Block device—/dev/dsk/emcpower#[a-h]
◆ Raw device—/dev/rdsk/emcpower#[a-h]
where:
◆ # is the disk number.
◆ [a-h] is the slice.
Slices in Sys V identifiers are designated s0, s1, s2, and so on. They
correspond exactly to emcpower slices designated a, b, c, and so on.
Therefore, if device
c0t0d0 corresponds to device emcpower0, slice
c0t0d0s2 corresponds to slice emcpower0c.
Selecting a Device
Naming Convention
After PowerPath is installed, a host has both native devices and
emcpower devices enabled and available for use. Both native devices
and emcpower devices can be active simultaneously on a host.
Native devices are preferable for most installations. Native devices
offer the following advantages:
◆ If PowerPath is installed, VxVM automatically scans for and
recognizes native devices when it (VxVM) is installed. (Pseudo
devices must be referenced manually when initializing disks for
use with VxVM.)
◆ If both PowerPath and VxVM are installed, VxVM automatically
scans for and recognizes native devices when volumes are
imported. (With pseudo devices, extra manual steps are required
to set up disk groups that can be imported.)
◆ VxVM provides unqualified support for native names. (VxVM
supports pseudo names with the following qualification: pseudo
names cause VxVM 3.2 to generate warnings in some
circumstances. This is a recognized VERITAS bug, 85455, and
EMC has a documented workaround. For details, see
http://seer.support.veritas.com/docs/242612.htm.)
◆ Existing applications, like volume managers and DBMSs, need
not be modified to provide PowerPath multipathing and path
failover functionality, because they can directly access PowerPath
logical devices through native devices. (With pseudo devices,
existing applications need to be modified to use this
functionality.)