AnalyticDB for PostgreSQL optimizes the I/O performance of compute nodes for instances created on May 19, 2021 and later. The query performance is improved by about 30%.

Release date

May 19, 2021.

Precautions

  • This optimization applies only to instances that are created on May 19, 2021 and later.
  • The resource type of instances must be set to Elastic Storage Mode.

Relationship between compute node specifications and I/O performance improvement

Compute node specifications Theoretical I/O performance improvement
2C16G 33%
4C32G 50%

I/O performance comparison between instances before and after this optimization

The performance of instances before and after this optimization is compared. In this example, two instances that have the following configurations are used:

  • Compute node specifications: 2C16GB
  • Number of compute nodes: 4
  • Storage capacity of compute nodes: 400 GB

The total computing and storage resources and their costs are the same between the two instances. The following example compares the query results of a SELECT COUNT(*) statement executed on an 80 GB table from each instance:

  • The following figure shows the query results of the instance created before May 19, 2021. Instance before this optimization
  • The following figure shows the query results of the instance created on May 19, 2021 or later. Instance after this optimization

The preceding example shows that SQL queries such as SELECT COUNT(*) are accelerated by about 30% after this I/O performance optimization.

Relationship between storage capacity and I/O performance

The following figure shows the results of a test that uses a 4C32G instance.

Relationship between storage capacity and I/O performance

The preceding figure shows that the I/O throughout is related to the storage capacity of compute nodes. The I/O throughput can reach the theoretical I/O bandwidth only when the storage capacity is greater than its specified threshold. If the storage capacity is less than this threshold, the I/O throughput changes linearly with the disk size.

To achieve the maximum I/O performance, we recommend that you set the storage capacity of compute nodes to 150 GB or more for 4C32GB instances.

The preceding relationship also applies to 2C16GB instances. The I/O bandwidth of 2C16GB instances is lower than that of 4C32GB instances. You can set the storage capacity of compute nodes to 50 GB or more to achieve the maximum I/O performance of 2C16GB instances.