How Veritas Volume Manager works

Databases require their storage media to be robust and resilient to failure. It is vital to protect against hardware and disk failures and to maximize performance using all the available hardware resources. Using a volume manager provides this necessary resilience and eases the task of management. A volume manager can help you manage hundreds of disk devices and makes spanning, striping, and mirroring easy.

Veritas Volume Manager (VxVM) builds virtual devices called volumes on top of physical disks. Volumes are accessed by a file system, a database, or other applications in the same way physical disk partitions would be accessed. Using volumes, VxVM provides the following administrative benefits for databases:

Table: Veritas Volume Manager features

Feature

Benefit

Spanning of multiple disks

Eliminates media size limitations.

Striping

Increases throughput and bandwidth.

Mirroring or RAID-5

Increases data availability.

Online relayout

Allows volume layout changes without application or database downtime. Online relayout can be used to change performance or reliability characteristics of underlying storage.

Volume resynchronization

Ensures that all mirrors contain exactly the same data and that the data and parity in RAID-5 volumes agree.

Dirty Region Logging (DRL)

Speeds the recovery of mirrored volumes after a system crash.

Volume snapshots

Allows backup of volumes based on disk mirroring.

VxVM provides full-sized and space-optimized instant snapshots, which are online and off-host point-in-time copy solutions.

FastResync

Separately licensed, optional feature that performs quick and efficient resynchronization of stale mirrors.

FastResync is included with the Enterprise Edition and is also included as part of the Veritas FlashSnap option with the Standard Edition.

Disk group split and join

Separately licensed, optional feature that supports general disk group reorganization and allows you to move volume snapshots to another host for off-host backup.

Disk group split and join is included with the Enterprise Edition and is also included as part of the Veritas FlashSnap option with the Standard Edition.

Hot-relocation

Automatically restores data redundancy in mirrored and RAID-5 volumes when a disk fails.

Dynamic multipathing (DMP)

Allows for transparent failover, load sharing, and hot plugging of physical disks.

Volume sets

Allows several volumes to be represented by a single logical mount device.

Dynamic LUN Expansion

Allows you to resize a disk after it has been initialized while preserving the existing data on the disk.

Storage Expert

Helps diagnose configuration problems with VxVM.

Cluster Volume Manager (CVM)

Separately licensed, optional feature that allows you to use VxVM in a cluster environment.

Veritas Volume Replicator (VVR)

Separately licensed, optional feature that provides data replication for disaster recovery solutions.

Free space pool management

Simplifies administration and provides flexible use of available hardware.

Online administration

Allows configuration changes without system or database down time.

For a more detailed description of VxVM and its features, refer to the Veritas Volume Manager Administrator's Guide.