Introduction to Volumes

You can use volumes to enforce disk usage limits, set replication levels, establish ownership and accountability, and measure the cost generated by different projects or departments. Create a volume for each user, department, or project. You can mount volumes under other volumes to build a structure that reflects the needs of your organization. Sub-volumes are created by mounting a volume in a sub-directory of an already mounted volume. This establishes a parent-child relationship between the volumes whereas the parent volume is mounted in top-level directory and the child volume is mounted in the sub-directory. The volume structure defines how data is distributed across the nodes in your cluster. Create multiple small volumes with shallow paths at the top of your cluster's volume hierarchy to spread the load of access requests across the nodes.

On a cluster with an Enterprise Edition or Enterprise Database Edition license, you can create a special type of volume called a mirror, a local or remote read-only copy of an entire volume. Mirrors are useful for load balancing or disaster recovery. You can also create a snapshot, an image of a volume at a specific point in time. Snapshots are useful for rollback to a known data set. You can create snapshots and synchronize mirrors manually or using a schedule.

The following sections provide introductory information about volumes: