Glossary

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A

addressable storage

The storage space encompassing online, nearline, offsite, and offline storage that is user-referenced through a Sun StorEdge QFS or Sun StorEdge SAM-FS file system.

archive media

The media to which an archive file is written. Archive media can be removable tape or magneto-optical cartridges in a library. In addition, archive media can be a mount point on another system.

archiver

The archive program that automatically controls the copying of files to removable cartridges.

archive storage

Copies of file data that have been created on archive media.

audit (full)

The process of loading cartridges to verify their VSNs. For magneto-optical cartridges, the capacity and space information is determined and entered into the automated library's catalog.

automated library

A robotically controlled device designed to automatically load and unload removable media cartridges without operator intervention. An automated library contains one or more drives and a transport mechanism that moves cartridges to and from the storage slots and the drives.

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B

backup storage

A snapshot of a collection of files for the purpose of preventing inadvertent loss. A backup includes both the file's attributes and associated data.

block allocation map

A bitmap representing each available block of storage on a disk and indicating whether the block is in use or free.

block size

See DAU.

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C

cartridge

A physical entity that contains media for recording data, such as a tape or optical disk. Sometimes referred to as a piece of media, a volume, or the medium.

catalog

A record of the VSNs in an automated library. There is one catalog for each automated library and, at a site, there is one historian for all automated libraries.

client-server

The model of interaction in a distributed system in which a program at one site sends a request to a program at another site and awaits a response. The requesting program is called the client. The program satisfying the response is called the server.

connection

The path between two protocol modules that provides reliable stream delivery service. A TCP connection extends from a TCP module on one machine to a TCP module on the other.

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D

data device

In a file system, a device or group of devices upon which file data is stored.

DAU

Disk allocation unit. The basic unit of online storage. Also called block size.

device logging

A configurable feature that provides device-specific error information used to analyze device problems.

device scanner

Software that periodically monitors the presence of all manually mounted removable devices and that detects the presence of mounted cartridges that can be requested by a user or other process.

direct access

A file attribute (stage never) designating that a nearline file can be accessed directly from the archive media and need not be retrieved to disk cache.

direct attached library

An automated library connected directly to a server using a SCSI interface. A SCSI-attached library is controlled directly by the Sun StorEdge SAM-FS software.

direct I/O

An attribute used for large block-aligned sequential I/O. The `setfa`(1) command's `-D` option is the direct I/O option. It sets the direct I/O attribute for a file or directory. If applied to a directory, the direct I/O attribute is inherited.

directory

A file data structure that points to other files and directories within the file system.

disk allocation unit

See DAU.

disk buffer

In a Sun SAM-Remote configuration, the buffer on the server system that is used for archiving data from the client to the server.

disk cache

The disk-resident portion of the file system software, used to create and manage data files between online disk cache and archive media. Individual disk partitions or an entire disk can be used as disk cache.

disk space threshold

The maximum or minimum level of disk cache utilization, as defined by an administrator. The releaser controls disk cache utilization based on these predefined disk space thresholds.

disk striping

The process of recording a file across several disks, thereby improving access performance and increasing overall storage capacity. See also striping.

drive

A mechanism for transferring data to and from a removable media volume.

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E

Ethernet

A local-area, packet-switched network technology. Originally designed for coaxial cable, it is now found running over shielded, twisted-pair cable. Ethernet is a 10- or 100-Mbytes/second LAN.

extent array

The array within a file's inode that defines the disk location of each data block assigned to the file.

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F

family device set

See family set.

family set

A storage device that is represented by a group of independent physical devices, such as a collection of disks or the drives within an automated library. See also storage family set.

FDDI

Fiber-distributed data interface is a standard for data transmission in a local area network that can extend in range up to 200 km (124 miles). The FDDI protocol is based on the token ring protocol.

Fibre Channel

The ANSI standard that specifies high-speed serial communication between devices. Fibre Channel is used as one of the bus architectures in SCSI-3.

file system

A hierarchical collection of files and directories.

file-system-specific directives

Archiver and releaser directives that follow global directives in the `archiver.cmd` file, are specific to a particular file system, and begin with
`fs =`. File-system-specific directives apply until the next `fs =` directive line or the end of file is encountered. If multiple directives affect a file system, the file-system-specific directives override the global directives.

FTP

File transfer protocol. An Internet protocol for transferring files between two hosts over a TCP/IP network.

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G

global directives

Archiver and releaser directives that apply to all file systems and that appear before the first `fs =` line.

grace period

For disk quotas, the amount of time for which a user is allowed to create files and allocate storage after reaching the soft limit.

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H

hard limit

For disk quotas, the maximum limit on file system resources, blocks, and inodes that users cannot exceed.

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I

indirect block

A disk block that contains a list of storage blocks. File systems have up to three levels of indirect blocks. A first-level indirect block contains a list of blocks used for data storage. A second-level indirect block contains a list of first-level indirect blocks. A third-level indirect block contains a list of second-level indirect blocks.

inode

Index node. A data structure used by the file system to describe a file. An inode describes all the attributes associated with a file other than the name. The attributes include ownership, access, permission, size, and the file location on the disk system.

inode file

A special file (`.inodes`) on the file system that contains the inode structures for all files resident in the file system. Inodes are 512 bytes long. The inode file is a metadata file, which is separated from file data in the file system.

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K

kernel

The central controlling program that provides basic system facilities. The UNIX kernel creates and manages processes, provides functions to access the file system, provides general security, and supplies communication facilities.

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L

LAN

Local area network.

lease

A function that grants a client host permission to perform an operation on a file for a specified period of time. The metadata server issues leases to each client host. The leases are renewed as necessary to permit continued file operations.

library

See automated library.

library catalog

See catalog.

local file system

A file system that is installed on one node of a Sun Cluster system and is not made highly available to another node. Also, a file system that is installed on a standalone server.

LUN

Logical unit number.

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M

`mcf`

Master configuration file. The file that is read at initialization time that defines the relationships between the devices (the topology) in a file system environment.

media

Tape or optical disk cartridges.

media recycling

The process of recycling or reusing archive media with few active files.

metadata

Data about data. Metadata is the index information used to locate the exact data position of a file on a disk. It consists of information about files, directories, access control lists, symbolic links, removable media, segmented files, and the indexes of segmented files.

metadata device

A device (for example, a solid-state disk or mirrored device) upon which file system metadata is stored. Having file data and metadata on separate devices can increase performance. In the `mcf`(4) file, a metadata device is declared as an `mm` device within an `ma` file system.

mirror writing

The process of maintaining two copies of a file on disjointed sets of disks to prevent loss from a single disk failure.

mount point

The directory on which a file system is mounted.

multireader file system

A single-writer, multireader capability that enables you to specify a file system that can be mounted on multiple hosts. Multiple hosts can read the file system, but only one host can write to the file system. Multiple readers are specified with the `-o reader` option with the`mount`(1M) command. The single-writer host is specified with the `-o writer` option with the `mount`(1M) command. For more information on the `mount`(1M) command, see the `mount_samfs`(1M) man page.

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N

name space

The metadata portion of a collection of files that identifies the file, its attributes, and its storage locations.

nearline storage

Removable media storage that requires robotic mounting before it can be accessed. Nearline storage is usually less expensive than online storage, but it takes somewhat longer to access.

network attached automated library

A library, such as those from StorageTek, ADIC/Grau, IBM, or Sony, that is controlled using a software package supplied by the vendor. The Sun StorEdge SAM-FS file system interfaces with the vendor software using a Sun StorEdge SAM-FS media changer daemon designed specifically for the automated library.

NFS

Network file system. A file system distributed by Sun that provides transparent access to remote file systems on heterogeneous networks.

NIS

The Sun OS 4.0 (minimum) Network Information Service. A distributed network database containing key information about systems and users on the network. The NIS database is stored on the master server and all slave servers.

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O

offline storage

Storage that requires operator intervention for loading.

offsite storage

Storage that is remote from the server and is used for disaster recovery.

online storage

Storage that is immediately available, such as disk cache storage.

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P

partition

A portion of a device or a side of a magneto-optical cartridge.

preallocation

The process of reserving a contiguous amount of space on the disk cache for writing a file. Preallocation can be specified only for a file that is size zero. For more information, see the`setfa`(1) man page.

pseudo device

A software subsystem or driver with no associated hardware.

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Q

quota

The amount of system resources that a user is allowed to consume.

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R

RAID

Redundant array of independent disks. A disk technology that uses several independent disks to reliably store files. It can protect against data loss from a single disk failure, can provide a fault-tolerant disk environment, and can provide higher throughput than individual disks.

recycler

A Sun StorEdge SAM-FS utility that reclaims space on cartridges that is occupied by expired archive copies.

release priority

The priority according to which a file in a file system is released after being archived. Release priority is calculated by multiplication of various weights of file properties and then summation of the results.

releaser

A Sun StorEdge SAM-FS component that identifies archived files and releases their disk cache copies, thus making more disk cache space available. The releaser automatically regulates the amount of online disk storage according to high and low thresholds.

remote procedure call

See RPC.

removable media file

A special type of user file that can be accessed directly from where it resides on a removable media cartridge, such as magnetic tape or optical disk cartridge. Also used for writing archive and stage file data.

robot

The portion of an automated library that moves cartridges between storage slots and drives. Also called a transport.

round robin

A data access method in which entire files are written to logical disks in a sequential fashion. When a single file is written to disk, the entire file is written to the first logical disk. The second file is written to the next logical disk, and so on. The size of each file determines the size of the I/O.

See also disk striping and striping.

RPC

Remote procedure call. The underlying data exchange mechanism used by NFS to implement custom network data servers.

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S

`samfsdump`

A program that creates a control structure dump and copies all the control structure information for a given group of files. It is analogous to the UNIX`tar`(1) utility, but it does not generally copy file data. See also samfsrestore.

SAM-QFS

A configuration that combines the Sun StorEdge SAM-FS software with the Sun StorEdge QFS file system. SAM-QFS offers a high-speed, standard UNIX file system interface to users and administrators in conjunction with the storage and archive management utilities. It uses many of the commands available in the Sun StorEdge SAM-FS command set as well as standard UNIX file system commands.

`samfsrestore`

A program that restores inode and directory information from a control structure dump. See also samfsdump.

SCSI

Small Computer System Interface. An electrical communication specification commonly used for peripheral devices such as disk and tape drives and automated libraries.

small computer system interface

See SCSI.

soft limit

For disk quotas, a threshold limit on file system resources (blocks and inodes) that you can temporarily exceed. Exceeding the soft limit starts a timer. When you exceed the soft limit for the specified time, no further system resources can be allocated until you reduce file system use to a level below the soft limit.

staging

The process of copying a nearline or offline file from archive storage back to online storage.

storage family set

A set of disks that are collectively represented by a single disk family device.

storage slots

Locations inside an automated library in which cartridges are stored when not being used in a drive.

striped group

A collection of devices within a file system that is defined in the `mcf`(4) file as one or more `g` XXX devices. Striped groups are treated as one logical device and are always striped with a size equal to the disk allocation unit (DAU).

stripe size

The number of disk allocation units (DAUs) to be allocated before writing proceeds to the next device of a stripe. If the `stripe=0` mount option is used, the file system uses round-robin access, not striped access.

striping

A data access method in which files are simultaneously written to logical disks in an interlaced fashion. SAM-QFS file systems provide two types of striping: "hard striping," using stripe groups, and "soft striping," using the `stripe=`x mount parameter. Hard striping is enabled when a file system is set up, and requires the definition of stripe groups within the `mcf`(4) file. Soft striping is enabled through the `stripe=`x mount parameter, and can be changed for the file system or for individual files. It is disabled by setting `stripe=0`. Hard and soft striping can both be used if a file system is composed of multiple stripe groups with the same number of elements. See also round robin.

Sun SAM-Remote client

A Sun StorEdge SAM-FS system with a client daemon that contains a number of pseudodevices, and can also have its own library devices. The client depends on a Sun SAM-Remote server for archive media for one or more archive copies.

Sun SAM-Remote server

Both a full-capacity Sun StorEdge SAM-FS storage management server and a Sun SAM-Remote server daemon that defines libraries to be shared among Sun SAM-Remote clients.

superblock

A data structure in the file system that defines the basic parameters of the file system. The superblock is written to all partitions in the storage family set and identifies the partition's membership in the set.

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T

tar

Tape archive. A standard file and data recording format used for archive images.

TCP/IP

Transmission Control Protocol/Internet Protocol. The internet protocols responsible for host-to-host addressing and routing, packet delivery (IP), and reliable delivery of data between application points (TCP).

timer

Quota software that keeps track of the period starting when a user reaches a soft limit and ending when the hard limit is imposed on the user.

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V

volume

A named area on a cartridge for sharing data. A cartridge has one or more volumes. Double-sided cartridges have two volumes, one on each side.

volume overflow

A capability that enables the system to span a single file over multiple volumes. Volume overflow is useful for sites using very large files that exceed the capacity of their individual cartridges.

VSN

Volume serial name. In the context of archiving to removable media cartridges, the VSN is a logical identifier for magnetic tape and optical disk that is written in the volume label. In the context of archiving to disk cache, this is the unique name for the disk archive set.

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W

WORM

Write once read many. A storage classification for media that can be written only once but read many times.

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