Managing Storage Locations
Vertica storage locations are the paths to file destinations you designate to store data and temporary files. Every node in the cluster requires at least one area in which to store data and another separate area in which to store database catalog files. You set up these locations as part of installation and setup. (See Prepare Disk Storage Locations in Installing Vertica for disk space requirements.)
Important: While no technical issue prevents you from using CREATE LOCATION to add one or more Network File System (NFS) storage locations, Vertica does not support NFS data or catalog storage except for MapR mount points. You will be unable to run queries against any other NFS data. When creating locations on MapR file systems, you must specify ALL NODES SHARED.
How Vertica Uses Storage Locations
Every time you add data to the database or perform a DML operation, the new data is held in memory (WOS) and moved to storage locations on disk (ROS) at regular intervals. Depending on the configuration of your database, many ROS containers are likely to exist.
You can label the storage locations you create to reference them in object storage policies. If an object to store has no associated storage policy, Vertica uses the available storage location and default storage algorithms to store data . If the object has a storage policy, Vertica stores the data at the object's designated storage location. See Creating Storage Policies. If you no longer need a storage location, you can retire or drop it, as described in Retiring Storage Locations and Dropping Storage Locations.
Comparing Local and Shared Storage Locations
You can define two types of storage locations:
- Local—Stores data in a unique location for each node. Local is the default for a storage location. You do not have to specify it explicitly. This location is in a directory in a file system that the node can access, and is often in the node’s own file system. You can create a local storage location for a single node or for all nodes in the cluster. Cluster-wide storage locations are the most common type of storage. Vertica defaults to using a local cluster-wide storage location for storing all data. If you want it to store data differently, you must create additional storage locations.
- Shared—Stores data on a single file system to which all nodes in the cluster have access. This shared file system is often hosted outside of the cluster, such as on a distributed file system like HDFS. When you create a shared storage location, each node in the Vertica cluster creates its own subdirectory in the location. The separate directories prevent nodes from overwriting each other's data. Currently, Vertica supports only HDFS shared storage locations. You cannot use NFS as a Vertica shared storage location except when using MapR mount points. See Vertica Storage Location for HDFS in Integrating with Apache Hadoop for more information.
