RDS PostgreSQL IO performance burst-ApsaraDB RDS(RDS)-阿里云帮助中心

Background

Premium ESSD is a storage class supported by RDS PostgreSQL. It retains all features of enterprise SSDs (ESSDs) and adds IO performance burst, which delivers higher IOPS under high IO pressure without requiring additional storage capacity.

Feature overview

After enabling IO performance burst, the instance’s maximum IOPS and throughput limits increase:

Note

Enabling IO performance burst on the primary node automatically enables it on the secondary node. Read-only instances require separate enablement on their product pages.

Scenario	Maximum IOPS	Maximum throughput (MB/s)
IO performance burst disabled	`min{50000, instance type max IOPS, 1800 + 50 × storage space}`	`min{350, instance type max IO bandwidth, 120 + 0.5 × storage space}`
Burst enabled	`min{1000000, instance type max IOPS}`	`min{4000, instance type max IO bandwidth}`

Note

When throughput reaches its limit, it affects IOPS. Similarly, when IOPS reaches its limit, it affects throughput.
The formulas above do not apply to General-purpose instance types, which share resources and cannot guarantee maximum IOPS or IO bandwidth.
For maximum IOPS and IO bandwidth values by instance type, see RDS PostgreSQL primary instance type list.

Scenarios

Workload peaks, large transactions, full table scans, and large result sets can all increase IO load. When CPU, memory, and storage remain sufficient but IO utilization hits 100%, you typically must upgrade the instance configuration or storage class (for example, from PL1 to PL2).

Without an upgrade, exceeding the IO limit causes performance degradation, query timeouts, and connection failures.
Upgrading the instance configuration wastes CPU, memory, and storage capacity.
Upgrading the storage class meets IO needs temporarily, but wastes resources and cost after IO load drops.

IO performance burst solves these issues by automatically raising IO limits during high load and reverting to baseline when load decreases—delivering serverless-like IO scaling without wasted resources.

Benefits

Compared to upgrading instance configurations or storage classes, IO performance burst reduces costs:

Pay only for burst usage consumed.
Metered per second.
Includes a free quota—only excess usage incurs charges.

Billing

IO performance burst for Premium ESSD is free starting April 16, 2024 (Promotional announcement). After the promotion ends, billing applies but includes a free quota—only excess usage incurs charges.

Billing method

Premium ESSD cost = storage fee + IO performance burst fee

Storage fee: Charged for instance storage space. Supports subscription and pay-as-you-go, using the same billing method as PL1 ESSD (Billing items).

IO performance burst fee: Hourly IO performance burst fee for an instance = (total IO performance burst across all nodes − free quota) × unit price

Note

IO performance burst fees for RDS instances (including primary and secondary nodes) support only pay-as-you-go billing. Charges apply only when IO performance burst is enabled and usage exceeds the free quota.

Total IO performance burst across all nodes

RDS Series	Instance IO performance burst
Basic Edition	Single-node IO performance burst
High-availability series	Primary node IO performance burst + secondary node IO performance burst
Cluster Edition	Primary node IO performance burst + IO performance burst from all secondary nodes

Single-node IO performance burst calculation

Scenario	IO performance burst	Example
IOPS exceeds baseline IOPS, but throughput does not exceed baseline throughput	`(IOPS − baseline IOPS) × duration` Note Baseline IOPS matches the IOPS limit when IO performance burst is disabled.	If instance IOPS exceeds baseline IOPS by 4,000 for 2 seconds, IO performance burst = `4,000 × 2 = 8,000`.
Throughput exceeds baseline throughput, but IOPS does not exceed baseline IOPS	`(throughput − baseline throughput) × 1024 × duration ÷ 16` Note Baseline throughput matches the throughput limit when IO performance burst is disabled. Throughput is in MB/s. Duration is in seconds. 16 is the conversion coefficient.	If instance throughput exceeds baseline throughput by 8 MB/s for 2 seconds, IO performance burst = `8 × 1024 × 2 ÷ 16 = 1,024`.
Both IOPS and throughput exceed their baselines	`max{(IOPS − baseline IOPS) × duration, (throughput − baseline throughput) × 1024 × duration ÷ 16}` Note Throughput is in MB/s. Duration is in seconds.	If `(IOPS − baseline IOPS) × duration` = 8,000 and `(throughput − baseline throughput) × 1024 × duration ÷ 16` = 65,536, then final IO performance burst = 65,536.

Note

When the primary node generates burst IO, the secondary node generates a nearly identical burst amount to maintain data and service consistency.
Read-only instances require separate enablement. Billing follows the same rules as the primary node. If the read-only instance uses the high-availability series, its fee includes both primary and secondary node burst fees.

Free quota:

RDS provides a free usage quota for IO performance burst. Usage exceeding this quota is charged based on the product edition.

Product Series	Free quota
Basic Edition	300,000 IO/hour
High-availability series	600,000 IO/hour
Cluster Edition	800,000 IO/hour

Unit price for IO performance burst: CNY 0.02 per 10,000 IO

Note
If burst usage beyond the free quota is less than 10,000 IO, it is billed as 10,000 IO.

Billing example

Example scenario	RDS PostgreSQL instance details: Beijing region, high-availability series, 1000 GB storage. Baseline IOPS: 50,000. Burst rate: 20,000 IOPS. Burst lasts 40 seconds per hour. Occurs every hour for one month.

IO performance burst	800,000 IO/hour
Free quota	600,000 IO/hour
Excess usage	200,000 IO/hour
Unit price	CNY 0.02 per 10,000 IO
Actual IO performance burst fee	0.02 × (80 − 60) × 24 × 30 = CNY 288

This leads to the following cost comparison:

Note

Prices in this example are for reference only. Actual prices appear in the console.

Storage type	Storage unit price (CNY/month)	Storage fee (CNY)	IO performance burst fee (CNY)	Total cost (CNY/month)
Premium ESSD	1600	1600 × 1 = 1600	288	1600 + 288 = 1888
PL2 ESSD	3200	3200 × 1 = 3200	Not applicable	3200

Premium ESSD saves CNY 1,312 per month compared to PL2 ESSD: 3,200 − 1,888 = 1,312

Note

The shorter the high-IO-load duration, the more cost-effective Premium ESSD is compared to PL2 ESSD.

Enable or disable IO performance burst

Note

Enabling or disabling IO performance burst takes several minutes, depending on the instance’s read/write traffic.
No transient disconnections occur. In rare cases, IOPS may fluctuate slightly. Perform this during off-peak hours.

Go to the Instances page. In the top navigation bar, select the region in which the RDS instance resides. Then, find the RDS instance and click the ID of the instance.
In the Basic Information section, click Premium ESSD settings next to Storage Type. In the dialog box, toggle the IO performance burst switch on or off.

References

Other RDS PostgreSQL storage types: Storage types.
Premium ESSD overview: Premium ESSD.
Use Buffer Pool Extension (BPE) to improve IO performance during large-scale or frequent data reads and writes.
Use Data archiving to store cold data in OSS and reduce storage costs.

Related APIs

API

Description

ModifyDBInstanceSpec

To configure IO performance burst for Premium ESSD:

Set DBInstanceStorageType to general_essd (Premium ESSD).
Set BurstingEnabled to true to enable or false to disable.
Keep all other parameters (instance type, storage size, etc.) unchanged.