WOS and ROS storage in HP Vertica

Vertica is unique in many ways, one of which can be seen in its data storage model. Vertica uses two distinct structures for storing data: WOS storage (Write Optimized Row Storage), and ROS storage (Read Optimized Column Storage). These are explained as following below.

1. WOS :
In Vertica, WOS stands for Write Optimized Store. The WOS is an in-memory data storage structure optimized for low-latency data loading. It is designed to efficiently support INSERT, UPDATE, DELETE, and most COPY operations.

When you load data, it first goes into WOS (unless you use the COPY DIRECT statement). Records in WOS are stored without compression or indexing to support faster loading. 

2. ROS :
ROS on the other hand, is structured for fast reads. ROS stands for Read Optimized Store. It’s a highly optimized, read-oriented, disk storage structure.

ROS data is partitioned into sections called storage containers. A container is just a set of rows created by move out or COPY DIRECT statements and stored in a particular group of files.The bulk of the data in your database lives in ROS and is both sorted and compressed.