Glossary

This glossary includes terms for the IBM TotalStorage SAN Volume Controller.

This glossary includes selected terms and definitions from A Dictionary of Storage Networking Terminology (http://www.snia.org/education/dictionary), copyrighted 2001 by the Storage Networking Industry Association, 2570 West El Camino Real, Suite 304, Mountain View, California 94040-1313. Definitions derived from this book have the symbol (S) after the definition.

The following cross-references are used in this glossary:

See
Refers the reader to one of two kinds of related information:
  • A term that is the expanded form of an abbreviation or acronym. This expanded form of the term contains the full definition.
  • A synonym or more preferred term.
See also
Refers the reader to one or more related terms.
Contrast with
Refers the reader to a term that has an opposite or substantively different meaning.

A

agent code
An open-systems standard that interprets Common Information Model (CIM) requests and responses as they transfer between the client application and the device.
application server
A server program in a distributed network that provides the execution environment for an application program.

B

back-end storage
The physical storage site on the storage server where data is stored. A data storage unit, such as a volume, can be striped across several locations, whereas the data storage unit is presented to a host (on the front end) as just a single address or entity.
broadcasting
The sending of a message to everyone on the network.

C

CIM
See Common Information Model.
CIM Agent
The code that is comprised of common building blocks that can be used instead of proprietary software or device-specific programming interfaces to manage CIM-compliant devices. A CIM agent is made up of the following components:
  • agent code
  • CIM object manager (CIMOM)
  • client application
  • device
  • device provider
  • Service Location Protocol
See also agent code, CIM object manager (CIMOM), client application, device, device provider, and Service Location Protocol.
CIM object manager (CIMOM)
The common conceptual framework for data management that receives, validates, and authenticates the CIM requests from the client application. It then directs the requests to the appropriate component or service provider.
client application
A storage management program that initiates Common Information Model (CIM) requests to the CIM agent for the device.
cluster
A collection of computers that are interconnected (typically at high-speeds) for the purpose of improving reliability, availability, serviceability and/or performance (via load balancing). Often, clustered computers have access to a common pool of storage, and run special software to coordinate the component computers' activities. (S)
Common Information Model (CIM)
A set of standards developed by the Distributed Management Task Force (DMTF). CIM provides a conceptual framework for storage management and an open approach to the design and implementation of storage systems, applications, databases, networks, and devices.
continuous, synchronous, remote copy
A storage server function in which the secondary copy of a logical volume is constantly updated to match changes made to a primary logical volume. The primary and secondary volumes can be on the same storage server or on separate storage servers. See also Peer-to-Peer Remote Copy.
copy rules
An object that defines a given copy services solution (copy type) in its entirety, from the base copy type it uses to the actions it takes given certain events.
copy set
The set of volumes that make up a solution for a given copy type.
copy type
An indicator that identifies a Replication Manager session as either a point-in-time copy or a continuous, synchronous, remote copy.
co-server
A function of IBM TotalStorage Multiple Device Manager (MDM) that discovers components and relationships among the storage devices that MDM supports. The components that the co-server discovers include logical unit numbers, metadata servers, and clients.
counterpart SAN
A nonredundant portion of a redundant storage area network (SAN). A counterpart SAN provides all the connectivity of the redundant SAN but without the redundancy. Each counterpart SANs provides an alternate path for each SAN-attached device. See also redundant SAN.

D

datagram
A form of asynchronous messaging in which an application sends a message, but does not require a response.
DB2(R) Universal Database
An IBM program product that helps leverage information by delivering the performance, scalability, reliability, and availability needed for the most demanding applications.
device
  • In the CIM Agent, the storage server that processes and hosts client application requests.
  • IBM definition: A piece of equipment that is used with the computer and does not generally interact directly with the system, but is controlled by a controller.
  • HP definition: In its physical form, a magnetic disk that can be attached to a SCSI bus. The term is also used to indicate a physical device that has been made part of a controller configuration; that is, a physical device that is known to the controller. Units (virtual disks) can be created from devices after the devices have been made known to the controller.
Device Manager
One of three components that make up the IBM TotalStorage Multiple Device Manager (MDM). Device Manager uses the Service Location Protocol (SLP) on the IBM Director to discover storage devices, creates managed objects to represent these discovered devices, and provides the user with access to device configuration functionality.
device provider
A device-specific handler that serves as a plug-in for the Common Information Model (CIM); that is, the CIM object manager (CIMOM) uses the handler to interface with the device.
directory agent
In the Service Location Protocol (SLP), an optional component that simplifies SLP administration and improves SLP performance. The SLP directory agent is an intermediate tier in the SLP architecture and is placed between the user agents and the service agents. The user agents and the service agents communicate only with the directory agent instead of with each other. See also service agent and user agent.
disk controller
A device that coordinates and controls the operation of one or more disk drives and synchronizes the operation of the drives with the operation of the system as a whole. Disk controllers provide the storage that the cluster detects as managed disks (MDisks).
disk zone
A zone defined in the storage area network (SAN) fabric in which the SAN Volume Controller can detect and address the logical units that the disk controllers present.
Distributed Management Task Force (DMTF)
An organization that defines standards for the management of distributed systems. See also Common Information Model.
DMTF
See Distributed Management Task Force.
duplex
The state of a Replication Manager volume pair that occurs after a copy operation when the volume pair is synchronized.

E

ESS
See IBM TotalStorage Enterprise Storage Server.
ESS Specialist
A Web-based interface to the IBM TotalStorage Enterprise Storage Server (ESS). Performance Manager uses ESS Specialist to verify user access to an ESS before the user can create a data-collection task for that ESS. The ESS Specialist can also be used to establish a path between a logical subsystem (LSS) in a source ESS and an LSS in a target ESS for use in creating copy pairs.
exception state
A status condition that occurs if any volume pairs in the session received an error that resulted in a message ending in "E" or "W".
exception volume
A volume that is in an exception state.
extent
A unit of data that manages the mapping of data between managed disks and virtual disks.

F

FAStT Storage Server
A RAID controller device that contains fibre-channel interfaces that connect the host systems and the disk drive enclosures. The FAStT Storage Server provides high system availability through use of hot-swappable and redundant components.
fenced
Pertaining to a type of user-defined function or stored procedure that is defined to protect the database management system from modifications by the function.
FlashCopy service
In SAN Volume Controller, a copy service that duplicates the contents of a source virtual disk (VDisk) to a target VDisk. In the process, the original contents of the target VDisk are lost. See also point-in-time copy.

G

gauge
A user-defined, graphical or tabular presentation of performance data and performance exceptions. Gauges are saved in the Performance Manager database and retrieved upon request.

H

host zone
A zone defined in the storage area network (SAN) fabric in which the hosts can address the SAN Volume Controllers.
hot-swappable component
A hardware component of a server, such as a disk drive, that can be exchanged while the server is in operation.

I

IANA
See Internet Assigned Numbers Authority.
IBM Director
A suite of tools and utilities that automates many of the processes required to manage systems, including capacity planning, asset tracking, preventive maintenance, diagnostic monitoring, and troubleshooting. It uses a graphical interface that provides easy access to both local and remote systems.
IBM TotalStorage Enterprise Storage Server (ESS)
An IBM product that provides an intelligent disk-storage subsystem across an enterprise.
IBM TotalStorage Multiple Device Manager (MDM)
A storage management software product that provides a single point of control across multiple supported storage devices on a storage area network (SAN). MDM services are provided by components that manage data storage. These components include Device Manager, Replication Manager, and Performance Manager. See also Device Manager, Replication Manager, and Performance Manager.
IBM TotalStorage SAN File System
A network-based, heterogeneous, file-storage system that provides file aggregation and data sharing in an open environment. The SAN File System is discovered by the IBM Director and is a managed object.
IBM TotalStorage SAN Volume Controller
A SAN appliance that attaches open-systems storage devices to supported open-systems hosts. The SAN Volume Controller provides symmetric virtualization by creating a pool of managed disks from the attached storage subsystems, which are then mapped to a set of virtual disks for use by various attached host computer systems.
IETF
See Internet Engineering Task Force
increment
A replication session copy function that performs another point-in-time (PIT) copy of the data in the selected session; any previous copy is lost. (The session is a PIT copy in the active state.) See also suspend (consistent), suspend (immediate), and terminate.
interactive mode
One of the three modes in the administrative command-line interface (CLI); this mode is used to run several commands by starting the CLI program and then specifying the commands at the program prompt. See also script modeand single-shot mode.
Internet Assigned Numbers Authority (IANA)
The organization that controls the assignment of internet protocol (IP) addresses.
Internet Engineering Task Force (IETF)
A large open international community of network designers, operators, vendors, and researchers concerned with evolution and smooth operation of the Internet, and responsible for producing Request for Comments (RFCs). The standards body responsible for Internet standards, including SNMP, TCP/IP, and policy for quality of service (QoS). The IETF has a web site at www.ietf.org. (S)
Internet Protocol (IP)
In the Internet suite of protocols, a connectionless protocol that routes data through a network or interconnected networks and acts as an intermediary between the higher protocol layers and the physical network.
IP
See Internet Protocol.
IP address
The unique 32-bit address that specifies the location of each device or workstation in the Internet. For example, 9.67.97.103 is an IP address.

J

job
A scheduled performance data collection task. A job consists of the tasks (such as the sampling frequency and duration) that are to be performed and the specified dates and times the job is to be performed. The job also includes the target systems or devices on which the job is to be performed.

L

logical subsystem (LSS)
The logical functions of a storage controller that allow one or more host I/O interfaces to access a set of devices. The controller aggregates the devices according to the addressing mechanisms of the associated I/O interfaces. One or more logical subsystems exist on a storage controller. In general, the controller associates a given set of devices with only one logical subsystem.
logical unit number
An identifier used on a SCSI bus to distinguish among devices (logical units) with the same SCSI ID.
lower interface
The portion of the IBM TotalStorage Enterprise Storage Server that is logically located below the device adapter.
LSS
See logical subsystem.
LUN
See logical unit number.

M

managed disk (MDisk)
A Small Computer System Interface (SCSI) logical unit that a redundant array of independent disks (RAID) controller provides and a cluster manages. The MDisk is not visible to host systems on the storage area network (SAN).
managed disk group
A collection of managed disks (MDisks) that, as a unit, contain all the data for a specified set of virtual disks (VDisks).
managed object (MO)
A component of a system that can be managed by a management application.
MDM
See IBM TotalStorage Multiple Device Manager.
metadata
Data that describes the characteristics of stored data; descriptive data.
MO
See managed object.
multicast
Transmission of the same data to a selected group of destinations.

N

node
An addressable entity connected to an I/O bus or network. Used primarily to refer to computers, storage devices, and storage subsystems. The component of a node that connects to the bus or network is a port. (S)

P

Peer-to-Peer Remote Copy (PPRC)
In SAN Volume Controller, a copy service that enables host data on a particular source virtual disk (VDisk) to be copied to the target VDisk designated in the relationship.
Performance Manager
One of three components that make up the IBM TotalStorage Multiple Device Manager (MDM). Performance Manager can be used to define a task for collecting performance data from a storage device that MDM supports. See also Device Manager and Replication Manager.
PIT
See point-in-time copy.
point-in-time (PIT) copy
An instant copy of data. See also FlashCopy.
pool
A named set of storage volumes that is the destination for storing client data.

R

RAID
See redundant array of independent disks.
random reads
A mode of reading data on a medium in a manner that requires the storage device to access nonconsecutive data on the medium.
random read cache hit
A request for nonconsecutive data while it is stored in cache.
random write destage
Movement of data from cache to nonconsecutive locations on a storage medium.
random writes
A mode of writing data on a storage medium in a manner that requires the storage device to access nonconsecutive locations on the medium.
redundant array of independent disks
A collection of two or more disk drives that present the image of a single disk drive to the system. In the event of a single device failure, the data can be read or regenerated from the other disk drives in the array.
redundant SAN
A storage area network (SAN) configuration in which any one single component might fail, but connectivity between the devices within the SAN is maintained, possibly with degraded performance. This configuration is normally achieved by splitting the SAN into two, independent, counterpart SANs. See also counterpart SAN.
replication element catalog
A repository of objects, such as devices, volumes, and other parts, that make up an environment that Replication Manager manages.
replication group
A collection of storage volumes grouped together so that they can be managed concurrently.
Replication Manager
One of three components that make up the IBM TotalStorage Multiple Device Manager (MDM). Replication Manager can be used to maintain consistent copies of data on source volumes that are managed by MDM. See also Device Manager and Performance Manager.
replication session
A concept within Replication Manager in which multiple pairs are handled as a consistent unit. You can use a replication session to create and manage copy relationships between source and target volume pairs or source volume groups, and among target pools.

S

script mode
One of the three modes available for use with the administrative command-line interface (CLI); this mode runs a set of commands that are defined in a file. See also interactive mode and single-shot mode.
SCSI
See Small Computer Systems Interface.
SCSI back-end layer
The layer in a Small Computer Systems Interface (SCSI) network that performs the following functions: controls access to individual disk controller systems that are managed by the cluster; receives requests from the virtualization layer, processes them, and sends them to managed disks; addresses SCSI-3 commands to the disk controller systems on the storage area network (SAN).
SCSI front-end layer
The layer in a Small Computer Systems Interface (SCSI) network that receives I/O commands sent from hosts and provides the SCSI-3 interface to hosts. SCSI logical unit numbers (LUNs) are mapped to virtual disks (VDisks) in this layer as well. Thus, the layer converts SCSI read and write commands that are addressed to LUNs into commands that are addressed to specific VDisks.
Secure Socket Layer (SSL)
A security protocol that provides transport layer security: authenticity, integrity, and confidentiality, for a secure connection between a client and a server. The protocol runs above TCP/IP and below application protocols.
sequence
Two volumes that exist as a pair in a replication session.
sequential reads
A mode of reading data on a storage medium in a manner that requires the storage device to access consecutive data on the medium.
sequential writes
A mode of reading data on a storage medium in a manner that requires the storage device to access consecutive locations on the medium.
service agent
In the Service Location Protocol, a software entity that is closely associated with one or more distinct network services. The service agent is responsible for making known the availability of these services upon request. See also directory agent and user agent.
Service Location Protocol (SLP)
In the Internet suite of protocols, a protocol that identifies and uses network hosts without having to designate a specific network host name.
shadowing
A function of Replication Manager in which a continuous backup copy of data is created using the continuous, synchronous, remote copy function. See also Peer-to-Peer Remote Copy.
single-shot mode
One of the three modes in the administrative command-line interface (CLI); this mode is used to run a single command by starting the CLI program and then specifying the command at the shell prompt. See also interactive mode and script mode.
SLP
See Service Location Protocol.
SMI-S
See Storage Management Initiative Specification.
Small Computer System Interface (SCSI)
A standard hardware interface that enables a variety of peripheral devices to communicate with one another.
SQL
See Standardized Query Language.
SSID
See subsystem identifier.
SSL
See Secure Socket Layer.
Structured Query Language (SQL)
A standardized language for defining and manipulating data in a relational database.
storage area network (SAN)
A network whose primary purpose is the transfer of data between computer systems and storage elements and among storage elements. A SAN consists of a communication infrastructure, which provides physical connections, and a management layer, which organizes the connections, storage elements, and computer systems so that data transfer is secure and robust. (S)
storage group
A collection of storage units that jointly contain all the data for a specified set of storage units, such as volumes. The storage units in a group must be from storage devices of the same type.
Storage Management Initiative Specification (SMI-S)
A design specification developed by the Storage Networking Industry Association (SNIA) that specifies a secure and reliable interface that allows storage management systems to identify, classify, monitor, and control physical and logical resources in a storage area network. The interface is intended as a solution that integrates the various devices to be managed in a storage area network (SAN) and the tools used to manage them.
storage pool
An aggregation of storage resources on a storage area network (SAN) that have been set aside for a particular purpose.
storage units
Data storage containers, such as volumes and logical unit numbers (LUNs).
subnet
An interconnected, but independent, segment of a network that is identified by its Internet Protocol (IP) address.
subsystem identifier (SSID)
A number that uniquely identifies a logical subsystem (LSS) within a computer installation.
suspend (consistent)
A replication session copy function that freezes the selected session, resulting in a consistent target copy if there are no errors. (The session is a continuous, synchronous, remote copy in the active state.) See also increment, suspend (immediate), and terminate.
suspend (immediate)
A replication session copy function that stops the selected session with no guarantee of consistency. (The session is a continuous, synchronous, remote copy in the active state.) See also increment, suspend (consistent), and terminate.
symmetric virtualization
A virtualization technique in which the physical storage in the form of Redundant Array of Independent Disks (RAID) is split into smaller chunks of storage known as extents. These extents are then concatenated, using various policies, to make virtual disks (VDisks). See also asymmetric virtualization.
synchronization-resynchronization process
The Replication Manager process that keeps a volume pair synchronized during a copy action.

T

terminate
A replication session copy function that stops the selected session and withdraws relationships. (The session is in the active state.) See also increment, suspend (immediate), and suspend (consistent).

U

UDP
See User Datagram Protocol.
unicast
Transmission of data to a single destination. Contrast with multicast.
Uniform Resource Locator (URL)
A sequence of characters that represent information resources on a computer or in a network such as the Internet. This sequence of characters includes (a) the abbreviated name of the protocol used to access the information resource and (b) the information used by the protocol to locate the information resource.
URL
See Uniform Resource Locator.
user agent
In the Service Location Protocol (SLP), a software entity that is closely associated with a client application or an end user who is looking for the location of a service on the network. The SLP user agent is responsible for finding the service for the user based on a general description of the desired service. See also directory agent and service agent.
User Datagram Protocol (UDP)
In the Internet suite of protocols, a protocol that provides unreliable, connectionless datagram service. It enables an application program on one machine or process to send a datagram to an application program on another machine or process. UDP uses the Internet Protocol (IP) to deliver datagrams.

V

VDisk
See virtual disk.
virtual disk (VDisk)
A set of disk blocks presented to an operating environment as a range of consecutively numbered logical blocks with disk-like storage and I/O semantics. The virtual disk is the disk array object that most closely resembles a physical disk from the operating environment's viewpoint. (S)
virtualization
In the storage industry, a concept in which a pool of storage is created that contains several disk subsystems. The subsystems can be from various vendors. The pool can be split into virtual disks that are visible to the host systems that use them.
vital product data (VPD)
Information that uniquely defines system, hardware, software, and microcode elements of a processing system.
volume performance advisor
A Performance Manager function that makes recommendations for setting performance requirements and allocating data storage to meet these requirements.
volume
A single unit of recording medium where information or data is recorded. The units are assigned to storage devices, such as the IBM TotalStorage Enterprise Storage Server.

W

WBEM
See Web-Based Enterprise Management.
Web-Based Enterprise Management (WBEM)
A tiered, enterprise-management architecture that was developed by the Distributed Management Task Force (DMTF). This architecture provides the management design framework that consists of devices, device providers, the object manager, and the messaging protocol for the communication between client applications and the object manager.
worldwide node name (WWNN)
An identifier for an object that is globally unique. WWNNs are used by Fibre Channel and other standards.
WWNN
See worldwide node name.

Z

zone
An area in a storage area network (SAN). The areas can be divided into a host zone and a disk zone. A connection in both zones allows an IBM TotalStorage SAN Volume Controller to access disk storage systems and host systems. See also host zone and disk zone.