Stub file
Encyclopedia
A stub file is a computer file
which appears to the user to be on disk
and immediately available for use but in fact some or all of the data of the file is being held on a different storage medium. When a stub file is accessed device driver
software intercepts the access, retrieves the data from its actual location and writes it to the file, and then allows the user's access to proceed. Typically the user is unaware that the file's data was being stored on a different medium although they may experience a slight delay when accessing such a file.
File stubbing, the act of creating stub files, is a Hierarchical storage management
(HSM) concept.
to enforce the use of low cost storage when users would prefer to store their files on the highest availability, and highest cost, media supplied.
, Novell NetWare
, Linux
and other operating systems.
Computer file
A computer file is a block of arbitrary information, or resource for storing information, which is available to a computer program and is usually based on some kind of durable storage. A file is durable in the sense that it remains available for programs to use after the current program has finished...
which appears to the user to be on disk
Disk storage
Disk storage or disc storage is a general category of storage mechanisms, in which data are digitally recorded by various electronic, magnetic, optical, or mechanical methods on a surface layer deposited of one or more planar, round and rotating disks...
and immediately available for use but in fact some or all of the data of the file is being held on a different storage medium. When a stub file is accessed device driver
Device driver
In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....
software intercepts the access, retrieves the data from its actual location and writes it to the file, and then allows the user's access to proceed. Typically the user is unaware that the file's data was being stored on a different medium although they may experience a slight delay when accessing such a file.
File stubbing, the act of creating stub files, is a Hierarchical storage management
Hierarchical storage management
Hierarchical storage management is a data storage technique which automatically moves data between high-cost and low-cost storage media. HSM systems exist because high-speed storage devices, such as hard disk drive arrays, are more expensive than slower devices, such as optical discs and magnetic...
(HSM) concept.
Purpose
The usual purpose of stubbing files is to move data from an expensive high-speed storage device such as a computer's hard drive to lower cost storage such as a magnetic tape, or an electro-optical disk, while not requiring users to know how to use specialised storage software to retrieve the data. It also allows a system managerSystem administrator
A system administrator, IT systems administrator, systems administrator, or sysadmin is a person employed to maintain and operate a computer system and/or network...
to enforce the use of low cost storage when users would prefer to store their files on the highest availability, and highest cost, media supplied.
Availability
Stubbing is a feature of many commercial file backup and archiving packages and is available for Microsoft WindowsMicrosoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
, Novell NetWare
Novell NetWare
NetWare is a network operating system developed by Novell, Inc. It initially used cooperative multitasking to run various services on a personal computer, with network protocols based on the archetypal Xerox Network Systems stack....
, Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
and other operating systems.
See also
- BridgeHead SoftwareBridgeHead SoftwareBridgeHead Software is a healthcare data and storage management software and services company. The parent company BridgeHead Software Limited is unquoted and registered in London, England. The group is headquartered in Ashtead, Surrey in the UK....
- Moonwalk (software)Moonwalk (software)Moonwalk is Enterprise HSM data management software developed by Moonwalk Inc.-Overview:The Moonwalk software allows scheduled data copy, move and migration of files. Files to be actioned are can be classified by location, name, size, age, owner and/or attributes.File migration to archival storage...
- OpenStore for File ServersOpenStore for File Servers"IBM Tivoli Storage Manager HSM for Windows" is an HSM product for Microsoft Windows which allows policy based archival of files out of NTFS and into IBM Tivoli Storage Manager. In its place is left a stub file with offline bit set and a matching reparse point. Access to the file is transparently...
- Reparse pointNTFS reparse pointAn NTFS reparse point is a type of NTFS file system object. It is available with the NTFS v3.0 found in Windows 2000 or later versions. Reparse points provide a way to extend the NTFS filesystem by adding extra information to the directory entry, so a file system filter can interpret how the...