This topic describes burstable performance instances, including their features, application scenarios, and concepts such as baseline performance, CPU credits, and performance modes. Burstable performance instances are able to burst above baseline CPU performance by using CPU credits.
When you use other types of Alibaba Cloud ECS instances, the number and performance metrics of the corresponding vCPUs are fixed, which means that you may be billed for unused computing resources. To resolve this issue, Alibaba Cloud offers burstable performance instances to help you build high-performance servers, at a low cost, for a wide range of scenarios that experience traffic spikes in specific time periods. Examples include stress test applications, light-load applications, microservices, and web application servers.
A burstable performance instance continuously accrues CPU credits. In this way, when higher CPU performance is required, the accrued CPU credits can be used without affecting the resource usage of applications deployed on the instance. For more information, see Baseline performance, Earn CPU credits, and CPU credit consumption.
CPU credits allow you to allocate computing resources according to the overall service landscape. The computing capability during off-peak hours can be reserved for peak hours, to make full use of CPU resources. If your network experiences traffic spikes, you can choose to enable the unlimited mode to ensure high performance. In the unlimited mode, if CPU credits are used in advance or overdrawn, additional fees may be charged. In the standard mode, if the instance has no remaining CPU credits, its CPU usage will not burst above the baseline performance. For more information, see Standard mode and Unlimited mode.
t5 instance type family
- Equipped with 2.5 GHz Intel Xeon processors
- The latest DDR4 memory
- No fixed ratio of vCPU to memory
- Baseline CPU performance, burstable, but restricted by accumulated CPU credits
- Resource balance among compute, memory, and networks
- Supports VPC network only
- Suitable for the following scenarios:
- Web application servers
- Lightweight web servers
- Development and testing environments
|Instance types||vCPU||Memory (GiB)||Avg baseline CPU performance||CPU credits/hour||Max CPU credit balance||Local disks (GiB)*||Bandwidth (Gbit/s)**||Packet forwarding rate (Thousand pps)***||NIC queues****||ENIs****||Private IP address of a single ENI|
Baseline performance enables a burstable performance instance to maintain steady CPU performance according to the selected instance type. That is, when the CPU usage equals the baseline performance, the instance earns the same CPU credits as it consumes. For more information, see the Avg baseline CPU performance column in t5 instance type family.
Earn CPU credits
CPU credits can be applied to adjust the computing capability of a burstable performance instance. The more credits that a burstable performance instance accrues, the more time it can burst beyond its baseline performance when higher performance is needed.
To ensure that you have sufficient CPU credits for running an instance, each vCPU is allocated 30 CPU credits after you create a burstable performance instance (called launch CPU credit). For example, an ecs.t5-lc1m2.large instance that is configured with two vCPUs receives 60 launch CPU credits after being created.
If a burstable performance instance earns more CPU credits than it consumes, the unused CPU credits are accrued in the CPU credit balance. The CPU credit balance can be retained for up to 24 hours to achieve a dynamic balance, which has an upper limit. For more information, see the Max. CPU credit balance column in t5 instance type family. For example, an ecs.t5-c1m1.large instance can earn 18 CPU credits per hour. Its maximum CPU credit balance is 432 (18 × 24 hours).
- If an instance is stopped but the No fees for stopped instances (VPC-Connected) feature is not enabled, the current CPU credit balance is unaffected and CPU credits continue to accrue.
- If an instance is stopped and the No fees for stopped instances (VPC-Connected) feature is enabled, the accrued CPU credits are lost and the instance stops accruing CPU credits until you restart the instance.
- If a Subscription instance expires, the current CPU credit balance is unaffected but the instance stops accruing CPU credits until you reactivate the instance.
- If the payment of a Pay-As-You-Go instance is overdue, the current CPU credit balance is unaffected but the instance stops accruing CPU credits until you clear the overdue payment.
CPU credit consumption
- One vCPU running at 100% usage for one minute
- One vCPU running at 50% usage for two minutes
- Two vCPUs running at 25% usage for two minutes
- If the CPU usage is lower than the baseline performance, the unused CPU credits are accrued in the CPU credit balance.
- If the CPU usage equals the baseline performance, the CPU credit balance remains unchanged.
- If the CPU usage is higher than the baseline performance, the instance consumes the accrued CPU credits.
A burstable performance instance running in the standard mode is suitable for scenarios where you do not usually, but occasionally require high CPU performance, such as lightweight web servers, development and testing environments, and low or mid-performance databases.
- Advance CPU credit: CPU credits that are used in advance but should be obtained within the next 24 hours. Advance CPU credits may incur fees. When an unlimited instance runs out of its CPU credit balance, advance CPU credits are used to deliver high CPU performance. When the CPU usage is lower than the baseline performance, the earned CPU credits are used to pay down (offset) the advance credits. For more information, see Impact of performance modes on billing.
- Overdrawn CPU credit: Additional CPU credits that are used to sustain high CPU usage after advance CPU credits are used up. Overdrawn CPU credits incur additional fees. For more information, see Impact of performance modes on billing.
The following figure illustrates how the unlimited mode works.
- Heavy-load occasions such as launch of new product functions or large-scale promotion on e-commerce platforms. You can enable the unlimited mode in peak hours and disable it in off-peak hours to reduce costs.
- Some websites experience traffic peaks in specific time periods, but the average CPU usage over a 24-hour period is lower than the baseline performance. You can keep the unlimited mode enabled to ensure use experience in peak hours. If CPU credits accrued in off-peak hours can pay down advance CPU credits, the overall website access experience can be guaranteed without incurring additional fees.
Create a burstable performance instance
- Instance type
- Image type: The smallest t5 instance ecs.t5-lc2m1.nano has a memory of 0.5 GiB. It supports only Linux variants or the Windows Server Version 1809 operating system. For more information, see Select an image.
- Network type: Only VPC is supported.
Change the instance type
You can replace your current burstable performance instance with other types of burstable performance instances or enterprise-level instances at any time. For more information, see Instance type families that support instance type upgrades.
Basic concepts related to CPU credits
|Launch CPU credit||Each burstable performance instance is allocated 30 launch CPU credits for each vCPU after you create a burstable performance instance.||For more information, see Earn CPU credits.|
|CPU credit balance||If a burstable performance instance earns more CPU credits than it consumes, the unused CPU credits are accrued in the CPU credit balance. If a burstable performance instance needs to burst above the baseline performance, it consumes the accrued credits.||For more information, see Earn CPU credits.|
|Max. CPU credit balance||The maximum number of credits that an instance can accrue within 24 hours. The CPU credit balance is retained for up to 24 hours to achieve a dynamic balance.||For more information, see Earn CPU credits.|
|Advance CPU credit||CPU credits that are used in advance but should be obtained within the next 24 hours. Advance CPU credits can be used only in the unlimited mode.||For more information, see Unlimited mode.|
|Overdrawn CPU credit||Additional credits required to maintain high performance after the advance CPU credits are used up. Overdrawn CPU credits incur fees and can be used only in the unlimited mode.||For more information, see Unlimited mode.|