RHSS:Definitions

Storage Concepts

File System
A subsystem of an operating system whose purpose is to provide long-term storage. The basic purpose of the file system is to represent and organize the operating system's available storage resources.

Virtual File System
A kernel software layer that handles all system calls related to the standard Linux file system. It provides a common interface to several kinds of filesystems.

Metadata
Information about a file, directory or device containing attributes such as user permissions, access control, device type, and time data. This information can also be about mount points for other file systems within the current file system, symbolic links, and so on.

Cluster
An arrangement of computers linked together to perform for users as a single coherent system.

Distributed File System
Leverage's a cluster to provide access to multiple storage devices. Sharing data is fundamental to all distributed systems.

Namespace
A term for a logical container created from the local storage. The namespace is leveraged by the distributed file system. It is a way to name things and organize them in a hierarchy.

Volume
A namespace presented as a POSIX mount point.

Scale Up Storage
Increases the capacity of the storage device, but only in a single dimension. An example might be adding additional disk capacity to a single computer in a cluster.

Scale Out Storage
increases the capability of a storage device in multiple dimensions. For example adding a server to a cluster increases CPU, disk capacity, and throughput for the cluster.

Userspace
Applications running in USERSPACE do not directly interact with hardware. Instead the kernel is leveraged to moderate access. Userspace applications are generally more portable than applications in kernel space.