# Displaying volume status for an Aurora PostgreSQL DB cluster In Amazon Aurora, a DB cluster volume consists of a collection of logical blocks. Each of these represents 10 gigabytes of allocated storage. These blocks are called *protection groups*. The data in each protection group is replicated across six physical storage devices, called *storage nodes*. These storage nodes are allocated across three Availability Zones (AZs) in the region where the DB cluster resides. In turn, each storage node contains one or more logical blocks of data for the DB cluster volume. For more information about protection groups and storage nodes, see [ Introducing the Aurora storage engine](https://aws.amazon.com/blogs/database/introducing-the-aurora-storage-engine/) on the AWS Database Blog. To learn more about Aurora cluster volumes in general, see [Amazon Aurora storage](Aurora.Overview.StorageReliability.md). Use the `aurora_show_volume_status()` function to return the following server status variables: + `Disks` — The total number of logical blocks of data for the DB cluster volume. + `Nodes` **—** The total number of storage nodes for the DB cluster volume. You can use the `aurora_show_volume_status()` function to help avoid an error when using the `aurora_inject_disk_failure()` fault injection function. The `aurora_inject_disk_failure()` fault injection function simulates the failure of an entire storage node, or a single logical block of data within a storage node. In the function, you specify the index value of a specific logical block of data or storage node. However, the statement returns an error if you specify an index value greater than the number of logical blocks of data or storage nodes used by the DB cluster volume. For more information about fault injection queries, see [Testing Amazon Aurora PostgreSQL by using fault injection queries](AuroraPostgreSQL.Managing.FaultInjectionQueries.md). **Note** The `aurora_show_volume_status()` function is available for Aurora PostgreSQL version 10.11. For more information about Aurora PostgreSQL versions, see [Amazon Aurora PostgreSQL releases and engine versions](AuroraPostgreSQL.Updates.20180305.md). **Syntax** ``` 1. SELECT * FROM aurora_show_volume_status(); ``` **Example** ``` customer_database=> SELECT * FROM aurora_show_volume_status(); disks | nodes -------+------- 96 | 45 ```