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

Abstract
This white paper discusses the next generation mass storage subsystem in HP-UX 11i v3. It is intended for system
administrators or operators who have experience with HP-UX and manage mass storage devices such as disks and
tape drives.
Publication History
• February 2007: Initial Publication
• September 2007: Addition of load balancing policies closest_path and pref_tport, coincident with
the September 2007 release of HP-UX 11i v3, Ignite-UX inventory blocking, and
corrected VxFS file system size
• April 2008: Addition of weighted_rr load balancing policy, coincident with the March 2008
release of HP-UX 11i v3, ioinit command changes
• May 2009: Addition of mediainit command and ioinit command changes
Background
HP-UX 11i v3 introduces a new representation of mass storage devices called the agile view. The central idea of
the agile view is that disk devices and tape drives are identified the actual object, not by a hardware path to the
object. Paths to a device can change dynamically, and multiple paths to a single device can be transparently
treated as a single virtualized path, with I/O distributed across those multiple paths. This representation increases
the reliability, adaptability, performance, and scalability of the mass storage stack, all without the need for
operator intervention.
This document addresses the following topics:
Features of the Next Generation Mass Storage Stack
Describes new mass storage functionality in HP-UX 11i v3. Major new features include scalability,
agile addressing, multi-pathing and load balancing, adaptability, and performance. Each section
includes background on previous supported features, reasons for the changes, and a summary of
user-visible changes.
Introduction to the Agile View
Describes the new mass storage user interfaces. This is a different take on the mass storage stack
features, and includes the new type of device special file (DSF) and new hardware addressing
model for mass storage.
Changes to I/O and Mass Storage Subsystems
Describes the effects on I/O commands. This includes new options for existing commands, new
commands, and changes to tunable parameters.
Changes to Other Subsystems
Describes the effects on HP-UX subsystems. This is a high-level description of the changes to
subsystems outside the I/O subsystem, such as LVM.
Migrating to the Agile View
Provides an overview of how to migrate applications, the kernel, and the system from the legacy
view to the agile view.
The paper concludes with a roadmap to other resources on the agile view and related changes.
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