1.4 Terminology

EVMS uses the following terminology in the EVMS user interface:

Table 1-2 EVMS Terms

Term

Description

Sector

The lowest level that can be addressed on a block device.

Disk

A physical disk or a logical device.

Segment

An ordered set of physically contiguous sectors on a single device. It is similar to traditional disk partitions.

Region

An ordered set of logically contiguous sectors that might or might not be physically contiguous. The underlying mapping can be to logical disks, disk segments, or other storage regions.

Feature

(Feature Object, EVMS Feature, EVMS Object)

A logically contiguous address space created from one or more disks, segments, regions, or other feature objects through the use of an EVMS feature.

Storage Object

Any storage structure in EVMS that is capable of being a block device. Disks, segments, regions, and feature objects are all storage objects.

Container

(Storage Container)

A collection of devices that is managed as a single pool of storage.

Private Storage Container: A storage container that is exclusively owned and accessed by only one server.

Cluster Storage Container: A storage container managed by the Cluster Resource Manager. It is accessible to all nodes of a cluster. An administrator can configure the storage objects in the cluster container from any node in the cluster. Cluster containers can be private, shared, or deported.

  • Private: The cluster container is exclusively owned and accessed by only one particular node of a cluster at any given time. The ownership can be reassigned by failover policies or the administrator.

  • Shared: The cluster container is concurrently owned and accessed by all nodes of a cluster. Shared containers are preferred for distributed databases, clustered file systems, and cluster-aware applications that can coordinate safe access to shared volumes.

  • Deported: The cluster container is not owned or accessed by any node of the cluster.

Volume

(Logical Volume)

A mountable storage object. Logical volumes can be EVMS volumes or compatibility volumes.

  • EVMS Volume: Volumes that contain EVMS metadata and support all EVMS features. Device nodes for EVMS volumes are stored in the /dev/evms directory. For example: /dev/evms/my_volume

  • Compatibility Volume: Volumes that are backward-compatible to other volume managers. They do not contain EVMS metadata and cannot support EVMS features.