ESSD AutoPL disks support I/O burst, which lets your cluster's input/output operations per second (IOPS) temporarily exceed its provisioned limit. This is useful when workloads are bursty by nature — steady under normal conditions, but spiking unpredictably for short intervals.
Common scenarios:
Batch processing at regular intervals — An accounting application processes daily transactions normally, then runs month-end reconciliation jobs that demand far higher disk throughput.
Traffic spikes — A web application receives steady traffic during the day but experiences sudden surges due to flash sales or marketing campaigns.
Scheduled data exports — A reporting pipeline runs large table scans at fixed intervals, requiring burst IOPS for minutes at a time.
This topic describes how to enable and disable I/O burst for the ESSD AutoPL disks of a PolarDB for MySQL cluster.
Limitations
Applies to PolarDB for MySQL clusters that use ESSD AutoPL disks.
Not supported for serverless clusters.
Enabling I/O burst on the primary node automatically enables it on all secondary nodes.
How it works
Enabling I/O burst raises both the maximum IOPS and maximum throughput of your cluster.
| Scenario | Maximum IOPS | Maximum throughput |
|---|---|---|
| I/O burst disabled | Does not exceed 50,000 | 350 MB/s |
| I/O burst enabled | Does not exceed 1,000,000 | Does not exceed 40,000 MB/s |
Throughput and IOPS are interdependent. When one reaches its limit, the other is also affected.
For the maximum IOPS and maximum I/O bandwidth values used in cluster specifications, see Compute node specifications for x86 architecture and Compute node specifications for YiTian ARM architecture.
IOPS calculation (PolarDB for MySQL Standard Edition):
IOPS = Maximum I/O bandwidth of the cluster specification (Gbit/s) × 1,024 × 1,024 ÷ 8 ÷ 16÷ 8: converts bits to bytes (1 byte = 8 bits)÷ 16: accounts for the 16 KB I/O operation size in PolarDB for MySQL
Disk performance formulas:
Baseline performance IOPS = 1,800 + 50 × Capacity (GiB)
Total disk IOPS = Baseline performance IOPS + Provisioned performance IOPS
Baseline performance throughput = 120 + 0.5 × Capacity (MB/s)
Provisioned performance throughput = 16 KB × Provisioned IOPS ÷ 1,024 (MB/s)
Total disk throughput = Baseline performance throughput + Provisioned performance throughput
Potential impacts
Enabling or disabling I/O burst does not cause transient disconnections and generally does not affect your services. In rare cases, cluster IOPS may fluctuate briefly. Perform this operation during off-peak hours.
The operation takes several minutes. The exact duration depends on current cluster usage, including read and write traffic.
Billing
An ESSD AutoPL disk incurs three types of fees:
| Fee type | When charged | Details |
|---|---|---|
| Disk capacity fees | When the disk is created | Same baseline performance pricing as a PL1 ESSD. See Billing rules for storage space. |
| Provisioned performance fees | Pay-as-you-go after the feature is enabled | Charged per provisioned IOPS, based on your zone configuration and billing method. |
| Performance burst fees | Pay-as-you-go when burst is active | USD 0.02 per 10,000 I/O operations. If the number of I/O operations is less than 10,000, it is rounded up to 10,000. |
Disk billing method | Disk fees (USD) | Cloud Disk Performance |
Subscription
Duration: 1 month |
|
|
Pay-as-you-go
Billing duration: 24 hours |
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The billable usage for an ESSD AutoPL disk includes basic storage space and provisioned IOPS.
Provisioned performance fees
Subscription
| Zone configuration | Fee |
|---|---|
| Single-zone (hot standby storage cluster disabled) | USD 0.006912/IOPS/month |
| Dual-zone (hot standby storage cluster enabled) | USD 0.011088/IOPS/month |
| Dual-zone (hot standby storage cluster and hot standby compute cluster enabled) | USD 0.011088/IOPS/month |
| Three-zone (hot standby storage cluster and logger node enabled) | USD 0.011088/IOPS/month |
Formula: Unit price × Subscription duration
Pay-as-you-go
| Zone configuration | Fee |
|---|---|
| Single-zone (hot standby storage cluster disabled) | USD 0.0000096/IOPS/hour |
| Dual-zone (hot standby storage cluster enabled) | USD 0.0000154/IOPS/hour |
| Dual-zone (hot standby storage cluster and hot standby compute cluster enabled) | USD 0.0000154/IOPS/hour |
| Three-zone (hot standby storage cluster and logger node enabled) | USD 0.0000154/IOPS/hour |
Billing duration: 24 hours
Performance burst fees
USD 0.02 per 10,000 I/O operations
I/O burst fees for all nodes (primary and secondary) are charged on a pay-as-you-go basis. Bills are generated hourly.
If the total I/O operations in a billing period are less than 10,000, the amount is rounded up to 10,000.
Enable I/O burst when creating a cluster
Go to the PolarDB cluster purchase page.
During cluster configuration, set Storage Type to ESSD AutoPL and turn on the I/O burst switch.
Enable or disable I/O burst for an existing cluster
Before you begin, confirm the following:
The cluster uses ESSD AutoPL disks.
I/O burst is not already in the state you want to set (enabling takes several minutes; avoid duplicate operations).
Off-peak hours are preferred to minimize the impact of potential IOPS fluctuation.
Steps:
Log on to the PolarDB console. In the upper-left corner, select the region where your cluster is deployed. Click the cluster ID.
In the Basic Information section, find the Distributed Storage section and click Change Storage Configuration.
On the Upgrade/Downgrade page, enter a value for Provisioned IOPS for AutoPL Disk as needed. For Enable I/O Burst, select Enable or Disable.
Set Switch Time:
Switch Now: The change takes effect immediately.
Scheduled Switch: Specify a time within the next 24 hours. The task completes within 30 minutes after the selected time. To view or cancel the task, go to the Scheduled Tasks page. For details, see Scheduled tasks.
Read and accept the relevant terms of service, then click Buy Now.
What's next
To view compute node specifications and performance parameters for your cluster, see Compute node specifications for x86 architecture.
To review storage billing rules, see Billing rules for storage space.