Disk space requirements for the database
In addition to actual data storage, the database requires disk space for several data reorganization operations, such as mergeout and managing nodes in the cluster. For best results, disk utilization per node should be no more than sixty percent (60%) for a K-Safe=1 database to allow such operations to proceed.
In addition, disk space is temporarily required by certain query execution operators, such as hash joins and sorts, in the case when they cannot be completed in memory (RAM). Such operators might be encountered during queries, recovery, refreshing projections, and so on. The amount of disk space needed (known as temp space) depends on the nature of the queries, amount of data on the node and number of concurrent users on the system. By default, any unused disk space on the data disk can be used as temp space. However, it is recommended that you provision temp space separate from data disk space.