Harmony (National
Research Council of Canada)
Harmony is a multitasking, multiprocessing operating
system for realtime control, developed at the National
Research Council to serve a need for a flexible system
for realtime control of robotics experiments and for
other applications of embedded systems where predictable
temporal performance is a requirement. Harmony is
extensible, configurable and portable, both across
different target computers (typically assembled from
single-board computers), and across different development
hosts.
Helios (Perihelion
Distributed Software)
Helios is a micro kernel operating system for embedded
and multiprocessor systems. The operating system is
modular in design and can scale from an embedded runtime
executive up to a fully distributed operating system.
Hive (Stanford University Flash Project)
The Hive OS Team is designing an operating system that is
able to operate effectively in a traditional
supercomputer environment as well as in a
general-purpose, multiprogrammed environment. The latter
environment poses significant challenges since
general-purpose environments typically contain large
numbers of processes making many system calls and many
small I/O requests.
HP 3000
(outdated)
HP 3000 MPE and MPE/iX
HPFS (OS/2 file system)
HPFS is the file system of OS/2,
distributed by IBM.
The High-Performance-Filesystem HPFS was obsolete right
at the time of its introduction into the market. It had
the
directories organized in multiple bands on the disk so
that the
physical ways for the heads on the disk were optimized in
directory-operations. Directories were placed in such a
way that the
mean way between data-area and directory-area was
optimized. The 3 main
time-consuming factors which slow down disk-acces should
get optimized
this way: step-time,head-settle-time and
disk-latency(this is the time
the disk needs to rotate until the desired sector is
under the head).
Although it gets easily forgotten that every cache has to
be filled at
least once before it can function as a cache(which means
on the other
hand that operations which reference an item only once
have no benefit
from caching), the upcomming of note-worthy caches but
more a new type
of disks made this system old-fashion: disks which show
to the outside
an geometry which is (very) different from their internal
real geometry.
This started when harddisks became intelligent and the
disk-manufacturers
could implement a variable-sector scheme to improve the
capacity of the
disk. It is clear that a system, which tries to optimize
physical ways
gets fooled by a disk which behaves in such a way. (The
sentence with
the cache-topic is not to be taken verbatim: caches are a
complex
subject. With read-ahead caches the statement may be
false!)
R.B.
HURD (Free Software
Foundation GNU Project)
Related to: Mach
The HURD is the operating system being developed by the
Free Software Foundation as the basis for the GNU
Project, which has already produced such well known tools
as Emacs and GCC. The Hurd is a personality for the Mach
micro-kernel which exports a bevy of services to the
application. The Hurd will provide the standard UNIX
interface, but should also be much more flexible than
standard UNIX.
Hurricane
The Hurricane operating system is a hierarchically
clustered operating system implemented on the Hector
multiprocessor. Hierarchical clustering manages the
system resources in clusters, using tight coupling within
a cluster, and loose coupling across clusters.
Distributed systems principles are applied by
distributing and replicating system services and data
objects to increase locality, increase concurrency, and
to avoid centralized bottlenecks, thus making the system
scalable.
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