Overview: The Next Generation Mass Storage Stack (September 2009)

Glossary
Agile Addressing
The ability to address a LUN with the same device special file regardless of the physical location of the
LUN or the number of paths leading to it. The DSF for a LUN remains the same even if the LUN is moved
from one HBA to another, moved from one switch or hub port to another, presented using a different
target port to the host, or configured with multiple hardware paths. Also referred to as persistent LUN
binding.
Agile View
The representation of LUNs using lunpath hardware paths, LUN hardware paths, and persistent DSFs,
introduced in HP-UX 11i v3.
DSF
Device Special File. A file associated with an I/O device. DSFs are read and written the same as
ordinary files, but requests to read or write result in activation of the associated device.
Hardware Path
A series of numbers representing the physical or virtualized location of a device. The path is a sequence
of I/O addresses that share a hierarchical relationship. The address elements may not correspond to
physical hardware addresses, and may represent only a “handle” to a device rather than a physical path
to it.
HBA
Host Bus Adapter. A physical I/O interface that provides I/O processing and connectivity between a
server and a storage device.
Legacy DSF
A DSF with the hardware path information such as SCSI bus, target, and LUN embedded in the file minor
name and file name, such as /dev/dsk/c#t#d#.
Legacy Hardware Path
The representation of a hardware path as it exists in releases prior to HP-UX 11i v3. It is composed of a
series of bus-nexus addresses separated by slashes (/) leading to the HBA. After the HBA, additional
address elements (such as domain, area, port, target, and LUN) are separated by periods (.). The string
0/2/1/0.1.4.0.0.2.7 is an example of a legacy hardware path.
Legacy View
The representation of legacy hardware paths and legacy DSFs as in releases prior to HP-UX 11i v3.
LUN
A SCSI logical unit. This refers to an end storage device such as a disk, tape, floppy, or CD. This is the
logical unit itself and does not represent the path to the logical unit.
LUN Hardware Path
A hardware path for a SCSI LUN that virtualizes all paths to the LUN. The first path element is 64000,
followed by a virtual bus instance and a logical unit number. Multi-pathed LUNs have a single LUN
hardware path. The string 64000/0xfa00.0x22 is an example of a LUN hardware path.
Lunpath
The physical hardware path leading to a SCSI logical unit. A SCSI LUN can have more than one lunpath.
38