Amazon Aurora storage
Following, you can learn about the Aurora storage subsystem. Aurora uses a distributed and shared storage architecture that is an important factor in performance, scalability, and reliability for Aurora clusters.
Topics
Overview of Amazon Aurora storage
Aurora data is stored in the cluster volume, which is a single, virtual volume that uses solid state drives (SSDs). A cluster volume consists of copies of the data across three Availability Zones in a single AWS Region. Because the data is automatically replicated across Availability Zones, your data is highly durable with less possibility of data loss. This replication also ensures that your database is more available during a failover. It does so because the data copies already exist in the other Availability Zones and continue to serve data requests to the DB instances in your DB cluster. The amount of replication is independent of the number of DB instances in your cluster.
Aurora uses separate local storage for nonpersistent, temporary files. This includes files that are used for such purposes as sorting large data sets during query processing, and building indexes. For more information, see Temporary storage limits for Aurora MySQL and Temporary storage limits for Aurora PostgreSQL.
What the cluster volume contains
The Aurora cluster volume contains all your user data, schema objects, and internal metadata such as the system tables and the binary log. For example, Aurora stores all the tables, indexes, binary large objects (BLOBs), stored procedures, and so on for an Aurora cluster in the cluster volume.
The Aurora shared storage architecture makes your data independent from the DB instances in the cluster. For example, you can add a DB instance quickly because Aurora doesn't make a new copy of the table data. Instead, the DB instance connects to the shared volume that already contains all your data. You can remove a DB instance from a cluster without removing any of the underlying data from the cluster. Only when you delete the entire cluster does Aurora remove the data.
Storage configurations for Amazon Aurora DB clusters
Amazon Aurora has two DB cluster storage configurations:
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Aurora I/O-Optimized – Improved price performance and predictability for I/O-intensive applications. You pay only for the usage and storage of your DB clusters, with no additional charges for read and write I/O operations.
Aurora I/O-Optimized is the best choice when your I/O spending is 25% or more of your total Aurora database spending.
You can choose Aurora I/O-Optimized when you create or modify a DB cluster with a DB engine version that supports the Aurora I/O-Optimized cluster configuration. You can switch from Aurora I/O-Optimized to Aurora Standard at any time.
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Aurora Standard – Cost-effective pricing for many applications with moderate I/O usage. In addition to the usage and storage of your DB clusters, you also pay a standard rate per 1 million requests for I/O operations.
Aurora Standard is the best choice when your I/O spending is less than 25% of your total Aurora database spending.
You can switch from Aurora Standard to Aurora I/O-Optimized once every 30 days. When you switch between Aurora Standard and Aurora I/O-Optimized storage options for non-NVMe-based DB instances, there is no downtime. However, for NVMe-based DB instances, switching between Aurora I/O-Optimized and Aurora Standard storage options requires a database engine restart, which may cause a brief period of downtime.
For information on AWS Region and version support, see Supported Regions and Aurora DB engines for cluster storage configurations.
For more information on pricing for Amazon Aurora storage configurations, see Amazon Aurora pricing
For information on choosing the storage configuration when creating a DB cluster, see Creating a DB cluster. For information on modifying the storage configuration for a DB cluster, see Settings for Amazon Aurora.
How Aurora storage automatically resizes
Aurora cluster volumes automatically grow as the amount of data in your database increases. The maximum size for an Aurora cluster volume is 128 tebibytes (TiB) or 64 TiB, depending on the DB engine version. For details about the maximum size for a specific version, see Amazon Aurora size limits. This automatic storage scaling is combined with a high-performance and highly distributed storage subsystem. These make Aurora a good choice for your important enterprise data when your main objectives are reliability and high availability.
To display the volume status, see Displaying volume status for an Aurora MySQL DB cluster or Displaying volume status for an Aurora PostgreSQL DB cluster. For ways to balance storage
costs against other priorities, Storage scaling describes how to monitor the
Amazon Aurora metrics AuroraVolumeBytesLeftTotal and VolumeBytesUsed
in CloudWatch.
When Aurora data is removed, the space allocated for that data is freed. Examples of removing data include dropping or truncating a table. This automatic reduction in storage usage helps you to minimize storage charges.
Note
The storage limits and dynamic resizing behavior discussed here apply to persistent tables and other data stored in the cluster volume.
For Aurora PostgreSQL, temporary table data is stored in the local DB instance.
For Aurora MySQL version 2, temporary table data is stored by default in the cluster volume for writer instances and in local storage for reader instances. For more information, see Storage engine for on-disk temporary tables.
For Aurora MySQL version 3, temporary table data is stored in the local DB instance or in the cluster volume. For more information, see New temporary table behavior in Aurora MySQL version 3.
The maximum size of temporary tables that reside in local storage is limited by the maximum local storage size of the DB instance. The local storage size depends on the instance class that you use. For more information, see Temporary storage limits for Aurora MySQL and Temporary storage limits for Aurora PostgreSQL.
Some storage features, such as the maximum size of a cluster volume and automatic resizing when data is removed, depend on the Aurora version of your cluster. For more information, see Storage scaling. You can also learn how to avoid storage issues and how to monitor the allocated storage and free space in your cluster.
How Aurora data storage is billed
Even though an Aurora cluster volume can grow up to 128 tebibytes (TiB), you are only charged for the space that you use in an Aurora cluster volume. In earlier Aurora versions, the cluster volume could reuse space that was freed up when you removed data, but the allocated storage space would never decrease. Now when Aurora data is removed, such as by dropping a table or database, the overall allocated space decreases by a comparable amount. Thus, you can reduce storage charges by dropping tables, indexes, databases, and so on that you no longer need.
Tip
For earlier versions without the dynamic resizing feature, resetting the storage usage for a cluster involved doing a logical dump and restoring to a new cluster. That operation can take a long time for a substantial volume of data. If you encounter this situation, consider upgrading your cluster to a version that supports dynamic volume resizing.
For information about which Aurora versions support dynamic resizing, and how to minimize storage charges by monitoring
storage usage for your cluster, see Storage scaling. For information about Aurora backup storage billing, see
Understanding Amazon Aurora backup storage usage. For pricing information about Aurora data
storage, see Amazon RDS for Aurora pricing
