You can use CPU credits to burst the performance of a burstable instance when required by your workloads. This topic describes the features, baseline performance, CPU credits, and performance modes of t5 and t6 burstable instances.

Scenarios

If you purchase an enterprise-grade instance, you have exclusive access to its vCPUs. While you enjoy the exclusive access, you must pay for vCPU resources regardless of whether you use the full performance of the vCPUs. Even if you only require high levels of computing power for a specific period during a day, you must pay for unused computing resources at other times during the day. To avoid this situation, you can select cost-effective and powerful burstable instances to better meet your business requirements.

Burstable instances are applicable to scenarios that require burstable performance for a specific period of time, such as stress testing service applications, lightweight applications, microservices, and web application servers. We recommend that you evaluate your business requirements to determine the performance levels required during off-peak and peak hours before you make a purchase decision. The baseline performance of the instances you purchase must at least meet your business requirements during off-peak hours. This way, you can experience the exact performance you want at a significantly lower cost. t5 and t6 burstable instances are available. For more information , see t5, burstable instance family and t6, burstable instance family.
Note If you find the burstable instance you have selected cannot meet your requirements after the instance is created, you can Change the configuration.

Features

You can accumulate CPU credits for your burstable instances, and consume these credits to increase the computing power of instances for your workloads when required. This consumption pattern does not affect the environments or applications running on your instances. For more information about baseline performance and CPU credits of burstable instances, see Baseline performance, Earn CPU credits, and Consume CPU credits.

Through the CPU credit mechanism, you can use more computing resources during peak hours and consume less computing resources during off-peak hours. If you have unplanned burstable performance requirements, you can enable the unlimited mode for your instances.

An instance in limited mode will run below its baseline performance if CPU credits are unavailable. However, a burstable instance in unlimited mode allows you to overdraw or pay for additional CPU credits and utilize CPU beyond its baseline performance at any time. In this case, you may be charged for the consumption of these additional CPU credits. For more information about the performance modes, see Standard mode and Unlimited mode.

Baseline performance

Baseline performance is an amount of vCPU capacity that is continuously provisioned to a burstable instance. The baseline performance varies depending on the instance type. If the vCPUs of your burstable instances are running at baseline performance, the CPU credits that you earn are equal to the CPU credits you consume. The Baseline CPU computing performance per vCPU column in the burstable instance family table indicates the baseline performance of a single vCPU.

Earn CPU credits

CPU credits are the computing resources that are available to be used. These computing resources determine the computing performance of your burstable instances.

After you create a burstable instance, 30 CPU credits are available for each vCPU of the instance, which are initial CPU credits. These credits allow you to complete deployment tasks after you start the instance. For example, an ecs.t5-lc1m2.large instance has two vCPUs. You will earn 60 CPU credits after you create one instance of this type. An ecs.t5-c1m1.xlarge instance has four vCPUs. You will earn 120 initial CPU credits after you create one instance of this type.

After you start a burstable instance, it starts to consume CPU credits to maintain its computing performance. At the same time, it also earns CPU credits at a fixed rate that is determined by the instance type. The CPU credits that a vCPU can earn per hour is based on its baseline performance. The CPU credits per hour column in the t5 instance type table indicates the CPU credits that all of the vCPUs of an instance can earn per hour. For example, 15% baseline performance of an ecs.t5-c1m1.large instance indicates that the CPU credits that a vCPU of the instance earns per hour can keep the vCPU running at 15% usage for an hour or at 100% usage for nine minutes (60 × 15%). In response to its baseline performance, each vCPU earns 9 CPU credits per hour. Therefore, an ecs.t5-c1m1.large instance with two vCPUs earns 18 CPU credits per hour.

If the CPU credits earned are more than the credits consumed, the net credits are accrued as CPU credit balance. CPU credit balance is valid within 24 hours to ensure the availability of CPU credits. A specific instance type earns CPU credits at a fixed rate. Therefore, its CPU credit balance is limited. The maximum CPU credit balance of a specific instance type is the CPU credits it can earn within 24 hours. For more information, see the Max CPU credit balance column in the burstable instance families table. For example, an ecs.t5-c1m1.large instance can earn 18 CPU credits per hour. This way, the maximum CPU credit balance it can earn is 432 (18 × 24).

In different scenarios, the shutdown of your instances may affect CPU credits:
  • If you still want to be charged after the instance shuts down, you can retain your current CPU credit balance and continue to earn credits.
  • If you do not want to be charged after the instance shuts down, your current CPU credit balance becomes invalid and you cannot continue to earn credits. After you restart your instances, you receive initial credits and start to earn credits again.
  • When a subscription instance expires, you can retain your current CPU credit balance, but you cannot continue to earn credits. When you restart the instance, you start to earn credits again.
  • For a pay-as-you-go instance, if your payment is overdue, you can retain your current CPU credit balance, but you cannot continue to earn credits until you complete the payment.

Consume CPU credits

The consumption rate of CPU credits of a burstable instance is based on the number of its vCPUs, CPU usage, and operating hours. For example, you consume one CPU credit in the following three scenarios:
  • A vCPU runs at 100% usage for a minute.
  • A vCPU runs at 50% usage for two minutes.
  • Two vCPUs run at 25% usage for two minutes.
When you start a burstable instance, it starts to consume CPU credits to maintain its computing performance. It first consumes initial credits which cannot be replenished when used up, and then consumes the accumulated CPU credits.
  • When your vCPUs run below baseline performance, the credits they earn are more than the credits they consume, resulting in an increase of CPU credit balance.
  • When your vCPUs run at baseline performance, the credits they earn equal the credits they consume, resulting in no change to the CPU credit balance.
  • When your vCPUs run above baseline performance, the credits they earn are less than the credits they consume, resulting in a decrease of CPU credit balance.

Standard mode

The performance of a burstable instance in limited mode is based on the availability of CPU credits. After it consumes all the initial credits and accrued credits, the instance cannot run above baseline performance. When the CPU credit balance is low, the instance gradually reduces CPU usage within 15 minutes until it runs at the baseline performance level. This way, the instance does not experience a sharp performance drop-off when its accrued CPU credit balance is depleted.
Note For more information about the relationship between the performance and CPU credits of a burstable instance in standard mode, see CPU credit change examples.

You can enable the standard mode for your instances if you have stable workloads and do not need instances to run beyond the baseline performance for an extended period of time. Otherwise, you may occasionally need to burst performance for scenarios, such as lightweight web servers, development and testing environments, and databases with low- and medium-performance.

Unlimited mode

The performance of a burstable instance in unlimited mode is not limited by the availability of CPU credits. You can overdraw or pay for additional CPU credits to utilize CPU above baseline performance at any time. If you keep running your instances above baseline performance when the initial CPU credits and accrued credits are all consumed, the CPU credits will vary as shown in the following figure. Two concepts involved in the figure are described as follows:
  • Advance CPU credits are credits that you pay for in advance and can receive within 24 hours after you make the payment.
  • Overdrawn CPU credits are used when you have consumed all the advance CPU credits to make sure that the instance is running beyond the baseline performance. You will be billed for using overdrawn credits.
Note For more information about the billing of burstable instances, see Billing.
Advance CPU credits and overdrawn CPU credits
Note For more information about the relationship between the performance and CPU credits of an instance in unlimited mode, see CPU credit change examples.
You can enable the unlimited mode for your instances if you need to consume advance CPU credits or overdrawn credits besides your credit balance to meet burstable performance requirements. For example:
  • You may expect substantial workloads to handle during certain events, such as new feature releases, e-commerce promotions, and website promotions that may require high CPU performance during a specific period. In this case, you can enable the unlimited mode for your instances and disable the mode to save costs when the workload spike ends.
  • Some web applications may require CPU bursts for a specific period during a day, but the daily average CPU usage is below the baseline CPU usage. In this case, you can enable the unlimited mode for your instances during peak hours to ensure positive customer experiences. If the CPU credits you earn during off-peak hours can offset the advance CPU credits consumed during peak hours, you can ensure overall positive customer experiences without paying extra fees.
Note When you create a burstable instance, the standard mode is enabled by default. For more information about how to enable unlimited mode, see Manage performance modes of a burstable performance instance.

Change the configuration

If you find the vCPUs keep running beyond or below the baseline performance level for an extended period of time when you monitor a burstable instance, this instance type cannot satisfy your business requirements. We recommend that you re-evaluate whether the instance type is suitable and select another burstable instance type or enterprise-level instance if necessary. For more information, see Instance families that support instance type changes.

Configuration changes of an instance vary according to its billing method.

t6, burstable instance family

Features:
  • Equipped with 2.5 GHz Intel ® Xeon ® Cascade Lake processors, with Turbo Boost up to 3.2 GHz
  • More cost-effective, compared with t5 burstable instance family
  • The maximum bandwidth can reach 6 Gbit/s
  • Paired with DDR4 memory
  • Provides baseline CPU performance and is burstable, but limited by accumulated CPU credits
  • Supports VPCs only
  • Suitable for the following scenarios:
    • Web application servers
    • Lightweight applications and microservices
    • Development and testing environments
The following table describes the instance types that belong to the t6 burstable instance family and specifications of these instance types.
Instance type vCPU Memory (GiB) Baseline CPU computing performance per vCPU CPU credits per hour Max CPU credit balance Local storage (GiB) Burstable bandwidth (Gbit/s) Packet forwarding rate (Kpps) IPv6 support NIC queues ENIs (including one primary ENI) Private IP addresses of a single ENI
ecs.t6-c4m1.large 2 0.5 5% 6 144 None 6.0 40 Yes 1 1 2
ecs.t6-c2m1.large 2 1.0 10% 12 288 None 6.0 60 Yes 1 1 2
ecs.t6-c1m1.large 2 2.0 20% 24 576 None 6.0 100 Yes 1 1 2
ecs.t6-c1m2.large 2 4.0 20% 24 576 None 6.0 100 Yes 1 1 2
ecs.t6-c1m4.large 2 8.0 30% 36 864 None 6.0 100 Yes 1 1 2
ecs.t6-c1m4.xlarge 4 16.0 40% 96 2,304 None 6.0 200 Yes 1 2 6
ecs.t6-c1m4.2xlarge 8 32.0 40% 192 4,608 None 6.0 400 Yes 1 2 6
Note

t5, burstable instance family

Features:
  • Equipped with 2.5 GHz Intel ® Xeon ® processors
  • Paired with DDR4 memory
  • Supports multiple CPU-to-memory ratios
  • Provides baseline CPU performance and is burstable, but limited by accumulated CPU credits
  • Offers a balance of compute, memory, and network resources
  • Supports VPCs only
  • Suitable for the following scenarios:
    • Web application servers
    • Lightweight applications and microservices
    • Development and testing environments
The following table lists the instance types that belong to the t5 instance family and specifications of these instance types.
Instance type vCPU Memory (GiB) Baseline CPU computing performance per vCPU CPU credits per hour Max CPU credit balance Local storage (GiB) Bandwidth (Gbit/s) Packet forwarding rate (Kpps) IPv6 support NIC queues ENIs (including one primary ENI) Private IP addresses of a single ENI
ecs.t5-lc2m1.nano 1 0.5 20% 12 288 None 0.1 40 Yes 1 1 2
ecs.t5-lc1m1.small 1 1.0 20% 12 288 None 0.2 60 Yes 1 1 2
ecs.t5-lc1m2.small 1 2.0 20% 12 288 None 0.2 60 Yes 1 1 2
ecs.t5-lc1m2.large 2 4.0 20% 24 576 None 0.4 100 Yes 1 1 2
ecs.t5-lc1m4.large 2 8.0 20% 24 576 None 0.4 100 Yes 1 1 2
ecs.t5-c1m1.large 2 2.0 25% 30 720 None 0.5 100 Yes 1 1 2
ecs.t5-c1m2.large 2 4.0 25% 30 720 None 0.5 100 Yes 1 1 2
ecs.t5-c1m4.large 2 8.0 25% 30 720 None 0.5 100 Yes 1 1 2
ecs.t5-c1m1.xlarge 4 4.0 25% 60 1,440 None 0.8 200 Yes 1 2 6
ecs.t5-c1m2.xlarge 4 8.0 25% 60 1,440 None 0.8 200 Yes 1 2 6
ecs.t5-c1m4.xlarge 4 16.0 25% 60 1,440 None 0.8 200 Yes 1 2 6
ecs.t5-c1m1.2xlarge 8 8.0 25% 120 2,880 None 1.2 400 Yes 1 2 6
ecs.t5-c1m2.2xlarge 8 16.0 25% 120 2,880 None 1.2 400 Yes 1 2 6
ecs.t5-c1m4.2xlarge 8 32.0 25% 120 2,880 None 1.2 400 Yes 1 2 6
ecs.t5-c1m1.4xlarge 16 16.0 25% 240 5,760 None 1.2 600 Yes 1 2 6
ecs.t5-c1m2.4xlarge 16 32.0 25% 240 5,760 None 1.2 600 Yes 1 2 6
Note

Terms of burstable instances

Term Description Reference
Initial CPU credits The CPU credits that you earn while creating a burstable instance. You can earn 30 credits for every vCPU. These credits cannot be replenished when used up. For more information, see Earn CPU credits.
CPU credit balance When the CPU credits earned are more than the credits consumed, the net credits are accrued as CPU credit balance. You can use these credits to run instances above baseline performance. For more information, see Earn CPU credits.
Max CPU credit balance The maximum CPU credit balance of a specific instance type is the CPU credits it can earn within 24 hours. CPU credit balance is valid for 24 hours to ensure the availability of CPU credits. A specific instance type earns CPU credits at a fixed rate. Therefore, its CPU credit balance is limited. For more information, see Earn CPU credits.
Advance CPU credits The CPU credits that you can pay for in advance and can receive within 24 hours after you make the payment. You must enable the unlimited mode before using advance CPU credits. For more information, see Unlimited mode.
Overdrawn CPU credits The CPU credits you use when you have consumed all advance CPU credits to make sure that the instance is running above baseline performance. You will be billed for using these credits. You must enable the unlimited mode before using overdrawn CPU credits. For more information, see Unlimited mode.