Glossary

ACS
Array Controller Software. The software and firmware that, together with the hardware, implements the features of StorageWorks array controllers. Different versions are optimized for specific applications; for example, ACS 8.5S provides a variety of features, including clone and snapshot.

Agent
In a client-server system, a program that performs information gathering or processing tasks on behalf of a client or server. Agents often communicate with other agents to perform a collective task on behalf of the user.

StorageWorks Agents run on a storage subsystem's host computer and can be accessed by StorageWorks clients to control and manage the storage subsystem.

Compaq Insight Manager Agents run on managed devices to monitor faults, performance and security, and to provide notification of changes in the device.

Application I/O Handler
In Enterprise Volume Manager, the feature that allows EVM to coordinate pre- and post-split procedures with an application program during the replication of storage units.

Backups

Full Backup. A backup of all selected files. The backup application does not check a file's last-changed date, but simply copies the file.

Incremental Backup. A backup of those selected files that are new or have changed since the last full backup. Also known as a cumulative-incremental backup.

Differential Backup. A backup of those selected files that are new or have changed since the last full or incremental backup. Also known as a differential-incremental backup.

Level Backup. In Legato NetWorker, a backup of those selected files that have changed since the last backup of any lower numbered level. The levels are numbered 1 through 9.

BCV
Business Continuance Volume. A generic term for a storage unit that is created from a standard production unit. A BCV unit can subsequently be used in production tasks such as: backups, application migration, data mining and testing. A key feature of a BCV unit is that it can be accessed while the production volume remains online for normal I/O. The term BCV unit does not imply the use of any specific technology.

Client
A computer or program that requests a service of another computer in a client-server system.

CLI
Command Line Interpreter or Interface. In StorageWorks, a text-oriented command line interface that enables configuration and monitoring of a storage subsystem by manually issuing commands to the array controller.

CLI Commands
The set of commands supported by StorageWorks Array Controller Software. For example, the command SHOW DISKS displays a list of disks attached to the controller.

Container
In StorageWorks, a logical volume identifier that the controller uses to represent disks in a storage set. For example, the container identifier M3 could represent a RAID 1 two-disk mirror set.

CLI Window
A StorageWorks application that enables configuration and monitoring of a storage subsystem via a graphical user interface.

Clone
In StorageWorks, a controller-based method of creating a physical copy of a storage unit. A duplicate member is created and the members of the mirror set are normalized to ensure that the data is identical on each member. During creation and normalization, the original unit remains online. Normalization of members is not instantaneous, but depends on factors such as disk size and I/O activity. Units created by the clone method are often used for tasks such as backups and application testing. The clone method cannot be used with RAID 3/5 units.

Command Console
StorageWorks Command Console (SWCC) is an application that allows configuration and monitoring of a storage subsystem. Its graphical user interface includes a Navigation Tree Window, Storage Window and CLI Window. Different versions of Command Console are optimized for specific applications.

Compaq Insight Manager
An application that uses Simple Network Management Protocol (SNMP) and Insight Management Agents to provide information about Compaq devices on a network. Insight collects information, such as device performance and alarms, and reports it to a management console.

Device
A hardware unit such as a computer, disk, tape, router, hub or adapter that can be attached to a host or network.

DLT
Digital Linear Tape. A magnetic tape technology that uses half-inch wide tape cartridges. The capacity of a DLT 4000 cartridge is 20 GB and a DLT 7000 is 35 GB.

ENSA
Enterprise Network Storage Architecture. Compaq ENSA is a high level architecture for the management of widely distributed storage assets. The individual devices, Storage Area Networks (SAN), and Network Attached Storage (NAS) in an enterprise can be managed as if they were a single, consolidated pool. ENSA provides the ability to modify storage configurations, to dynamically allocate storage to distributed application servers and to back up and restore application data with minimal interruption of application activity.

EVM Network. A network that consists of EVM-enabled computers that are connected to a common LAN and to an EVM-compatible StorageWorks subsystem.

Fibre Channel
A high speed, serial bus technology that supports channel and network architectures and a variety of transmission media and protocols. Fibre Channel Arbitrated Loop (FC-AL) is a standard designed for mass storage and other peripheral devices. It uses optical fiber to achieve transfer rates up to 1 GB per second.

Host
In StorageWorks, the controlling computer to which a storage subsystem is attached.

Initialization
In StorageWorks, the process of starting or restarting the storage subsystem's array controllers and establishing its configuration and operation. Also, the process of starting the replication of a storage unit.

Instance

The presence of a program or set of related programs in a computer or storage subsystem. In Enterprise Volume Manager there can be a server instance and a client instance.

JBOD
Just a Bunch of Disks. A term which indicates that one or more physical disks can be treated as individual, non-RAID units.

Job (EVM job)
A file created by Enterprise Volume Manager that represents the user's request to perform a task or series of tasks. For example, the EVM job named stor1_backup_daily_sales might: 1) replicate a storage units by the clone method to create BCV units, 2) mount the BCV units on a server and, 3) start the tape backup of the BCV units. EVM jobs are created by using the Create EVM Job page of the graphical user interface. Jobs can be run from the graphical user interface, via the EVM Command Line, from script files, or a scheduler.

LUN (logical unit number)
In a storage system, the value used to identify logical storage units of a SCSI target device.

Migration
Data migration is a generic term that refers to the transfer (physical copying) of large amounts of data from one storage device to another. System or application migration is a change from one system or application to another, or from one version to a significantly different version.

Mount Point
In UNIX, a mount point specifies the directory to use for mounting a device. For example, the
/usr directory could be the mount point for the disk device /dev/dsk/c0t1d0s6.

Mirroring (shadowing)
A generic term for data or program redundancy. In StorageWorks and RAID technology, a technique in which data is simultaneously recorded (duplicated) on separate physical disks. When the primary disk is offline or not functional, the alternate disk takes over to provide uninterrupted access.

Node
A generic term for an addressable unit, such as a computer or peripheral device attached to a network. In EVM, an EVM-enabled computer that is connected to the EVM Network.

Normalization
In StorageWorks, a process in which the members of a storage unit are written to and verified for identical content on a block-by-block basis.

RAID
Redundant Array of Independent Disks. A set of techniques for configuring and using an array of physical disks to provide fault tolerance and increase performance of a storage subsystem.

RAID Level
RAID techniques are identified by level numbers. Some common levels are:

Level Technique Applications
RAID 0 Striping High performance, but non-critical files
RAID 1 Mirroring System drives, critical files
RAID 0+1 Striping and mirroring Critical response time
RAID 3 Striping and parity Large I/O size
RAID 5 Striping and parity High request rate, read intensive data lookup

SAN
Storage Area Network. A dedicated, high-speed sub-network of storage devices that are available to servers on a LAN or WAN. As storage devices are added to the SAN they become accessible to the servers in the larger network.

SANworks
SANworks is a Compaq line of software products that provides storage management solutions, data protection and recovery, automatic performance tuning, storage virtualization and other features for multivendor storage environments.

Scheduler
An application that schedules and runs tasks. A typical scheduled task in the StorageWorks environment is running an EVM job that replicates storage units for use in tape backups.

Server
A computer or program that provides a service to other computers in a client-server system. Servers often run continuously waiting for requests from clients.

Slice (partition)
In UNIX, each file system is assigned to a slice (group of cylinders). Each slice appears to the operating system as a separate disk drive. Slices are also called partitions.

Snapshot (Virtual Replication)
In StorageWorks, a nearly instantaneous controller-based method of creating a virtual copy of a storage unit. During creation the original unit remains online and there is no interruption of operations. The virtual copy consists of a bitmap stored in the array controller cache (not on disk), and a temporary unit that holds data that have been over-written since the snapshot was created. Units created by the snapshot method are typically used to conduct short term tasks such as backups.

StorageWorks
StorageWorks is a Compaq line of hardware storage solutions for multivendor server environments.

Subsystem (Storage Subsystem)
From the perspective of a host, each addressable StorageWorks array controller pair (or single controller) and their attached physical disks.

Tape Library
A device that contains multiple tape drives. Tape libraries provide large scale storage and automated backup and restore capabilities.

TCP/IP
Transport Control Protocol / Internet Protocol. A suite of communications protocols used to connect host computers to the Internet.

Undo-Job
A special job file that is automatically created by Enterprise Volume Manager for the purpose of "undoing" steps that have been completed in a user-created job. For example, the job named undo_stor1_backup_daily_sales could be run after a tape backup was completed. The undo-job would unmount the BCV units and return their disks to the pool of free storage resources.

Unit
In StorageWorks, a logical volume identifier that the controller uses when a container is mounted on a host computer. For example, the unit identifier D1 could represent a RAID 0+1 striped mirror set that is mounted on a host computer. StorageWorks disk units begin with the letter D and tape units begin with the letter T.

Volume
A generic term for a storage unit such as a hard disk, floppy disk, disk cartridge, CD-ROM or tape cartridge.

WBEM
Web-based Enterprise Management. WBEM is a set of Internet technologies for exchanging information between management systems and applications. Standards allow applications to identify, access and report data regardless of the original source. The platform-independent approach utilizes a Web browser interface and HTML to communicate with devices.