Specifications

gigabyte (GB). A gigabyte of storage is 10
9
bytes. A
gigabyte of memory is 2
30
bytes.
GDPS. Geographically Dispersed Parallel Sysplex, an
S/390 multi-site application availability solution.
group. See disk drive module group or Copy Services
server group.
H
HA. See host adapter.
HACMP. Software that provides host clustering, so that
a failure of one host is recovered by moving jobs to
other hosts within the cluster; named for high-availability
cluster multiprocessing
hard disk drive (HDD). (1) A storage medium within a
storage server used to maintain information that the
storage server requires. (2) A mass storage medium for
computers that is typically available as a fixed disk
(such as the disks used in system units of personal
computers or in drives that are external to a personal
computer) or a removable cartridge.
Hardware Service Manager (HSM). An option
selected from System Service Tools or Dedicated
Service Tools on the AS/400 or iSeries host that
enables the user to display and work with system
hardware resources, and to debug input-output
processors (IOP), input-output adapters (IOA), and
devices.
HDA. See head and disk assembly.
HDD. See hard disk drive.
hdisk. An AIX term for storage space.
head and disk assembly (HDA). The portion of an
HDD associated with the medium and the read/write
head.
heartbeat. A status report sent at regular intervals
from the ESS. The service provider uses this report to
monitor the health of the call home process. See call
home, heartbeat call home record, and remote technical
assistance information network.
heartbeat call home record. Machine operating and
service information sent to a service machine. These
records might include such information as feature code
information and product logical configuration
information.
High Speed Link (HSL). Bus technology for
input-output tower attachment on iSeries host.
home address. A nine-byte field at the beginning of a
track that contains information that identifies the
physical track and its association with a cylinder.
hop. Interswitch connection. A hop count is the
number of connections that a particular block of data
traverses between source and destination. For example,
data traveling from one hub over a wire to another hub
traverses one hop.
host adapter (HA). A physical subunit of a storage
server that provides the ability to attach to one or more
host I/O interfaces. The Enterprise Storage Server has
four HA bays, two in each cluster. Each bay supports up
to four host adapters.
host processor. A processor that controls all or part of
a user application network. In a network, the processing
unit in which the data communication access method
resides. See host system.
host system. (1) A computer system that is connected
to the ESS. The ESS supports both mainframe (S/390
or zSeries) hosts as well as open-systems hosts. S/390
or zSeries hosts are connected to the ESS through
ESCON or FICON interfaces. Open-systems hosts are
connected to the ESS by SCSI or fibre-channel
interfaces. (2) The data processing system to which a
network is connected and with which the system can
communicate. (3) The controlling or highest level
system in a data communication configuration.
hot plug. Pertaining to the ability to add or remove a
hardware facility or resource to a unit while power is on.
HSL. See High Speed Link.
I
IBM Eserver. The brand name for a series of server
products that are optimized for e-commerce. The
products include the iSeries, pSeries, xSeries, and
zSeries.
IBM product engineering (PE). The third-level of IBM
service support. Product engineering is composed of
IBM engineers who have experience in supporting a
product or who are knowledgeable about the product.
IBM StorWatch Enterprise Storage Server Expert
(ESS Expert). The software that gathers performance
data from the ESS and presents it through a Web
browser.
IBM TotalStorage Enterprise Storage Server (ESS).
A member of the Seascape
®
product family of storage
servers and attached storage devices (disk drive
modules). The ESS provides for high-performance,
fault-tolerant storage and management of enterprise
data, providing access through multiple concurrent
operating systems and communication protocols. High
performance is provided by four symmetric
multiprocessors, integrated caching, RAID support for
the disk drive modules, and disk access through a
high-speed serial storage architecture (SSA) interface.
192 ESS Host Systems Attachment Guide
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