EMC 300-000-978 REV A03 manual Pseudo Devices, Selecting a Device, Naming Convention

5

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	After PowerPath is installed, a host has both native devices and
	Naming Convention	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.)
5-6	PowerPath for UNIX Installation and Administration Guide