HP-UX 11i v3 introduces a new representation of mass storage
devices, known as the agile view. In the agile view, disk devices
and tape drives are identified by the actual object, not by a hardware
path to the object. In addition, paths to the device can change
dynamically and multiple paths to a single device can be transparently
treated as a single virtualized path, with I/O being distributed
across those multiple paths.
This representation increases the reliability, adaptability,
performance, and scalability of the mass storage stack, without
the need for operator intervention.
HP-UX 11i v3 Hardware Paths
In HP-UX 11i v3, there are three different types of paths
to a device: legacy hardware path, lunpath hardware path, and LUN
hardware path. All three are numeric strings of hardware components,
with each number typically representing the location of a hardware
component on the path to the device. These paths are described below.
Legacy hardware
path
The legacy hardware path is the format used in releases prior to HP-UX
11i v3, and is displayed in the legacy view. It is composed of a series
of bus-nexus addresses separated by ‘/’ leading
to the host bus adapter (HBA); beyond the HBA, additional address
elements are separated by ‘.’.
Lunpath hardware path
The lunpath format enables the use of more targets
and LUNs than are permitted under legacy hardware paths, and is
printed in the agile view. It is identical in format to a legacy
hardware path, up to the HBA (and represents the same path to the
LUN). Beyond the HBA, additional elements are printed in hexadecimal.
LUN hardware path
The LUN format is a virtualized path that represents
all the lunpaths to a single LUN. It is printed in the agile view.
Instead of a series of bus-nexus addresses leading to the HBA, the
path contains a virtual bus-nexus (referred as the virtual root
node) with an address of 64000. An example of a LUN hardware path
is “64000/0xfa00/0x22”.
HP-UX 11i v3 Device Special File (DSF)
In a similar way to hardware paths, there are two types of
DSFs for mass storage: legacy DSFs and persistent DSFs. Both can
be used to access a given mass storage device independently, and
can coexist on a given system. These DSFs are described below.
A legacy device
special file was the only type of mass storage DSF in releases prior
to HP-UX 11i v3, so it is associated with the legacy view. It is
locked to a particular physical hardware path, or lunpath, and does
not support agile addressing. Each lunpath requires a different
DSF, so a multi-pathed LUN has multiple DSFs, one for each lunpath.
A persistent device special
file is associated with a LUN hardware path, and is seen in the
agile view. Because it is based on the LUN hardware path, rather
than the lunpath, it transparently supports agile addressing and
multipathing. Like the LUN hardware path, the binding of device
special file to device persists across reboots, but is not guaranteed
to persist across installations.
Device Files: Installing and Updating
If you cold-install HP-UX 11i v3, both legacy and persistent
DSFs are automatically created. By default, the installation process
will configure system devices like the boot, root, swap, and dump
devices to use persistent DSFs. This means that configuration files
such as /etc/fstab, /etc/lvmtab, and others will contain references to persistent DSFs.
If you update from HP-UX 11i v2 to 11i v3, existing legacy
DSFs are retained, and persistent DSFs will be created.
In addition, legacy DSFs are completely backward compatible,
and will not be affected by any persistent DSFs on the same server.
A device can be simultaneously accessed via legacy and persistent
DSFs.For more information on the new mass storage stack, see the
whitepaper called, “The Next Generation Mass
Storage Stack: HP-UX 11i v3” at:
http://docs.hp.com/
Printable version
