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Elastic Compute Service:Overview of instances

Last Updated:Aug 31, 2023

An Elastic Compute Service (ECS) instance is a virtual server that includes basic components such as vCPUs, memory, an operating system (OS), network configurations, and disks. You can use management tools provided by Alibaba Cloud, such as the ECS console and the ECS API, to create and manage ECS instances. You can manage the status of ECS instances and the applications deployed on the instances in the same manner as you would do with on-premises servers. You can also upgrade the capabilities of your ECS instances, such as compute and storage capabilities, as your requirements increase.

Basic instance configurations

The following basic configurations of each ECS instance determine the basic resources that the instance requires:

Instance type

Instance types comprise varying combinations of compute, memory, and storage capacities and allow you to choose an appropriate mix of resources for your applications. Instance types must be used together with images, Elastic Block Storage (EBS) devices, and network resources to create ECS instances that serve different purposes.

ECS provides a variety of instance families for common use scenarios. Each instance family consists of multiple instance types that have different compute capabilities to suit different scenarios and levels of requirements. For information about the available instance types, see Overview of instance families. For suggestions on how to select appropriate instance types for different scenarios, see Best practices for selecting instance types.

If you use on-premises servers, you may need to purchase new or replacement hardware as your compute needs change. This is costly and inconvenient. If you use ECS instances, you need only to upgrade or downgrade the instance types when your compute needs change. For more information, see Overview of instance configuration changes.


Images contain information that is required to run ECS instances, such as OSs and initialization data of applications. Alibaba Cloud provides ready-to-use OS images for Windows Server and mainstream Linux distributions. You can also create or import custom images to eliminate the need to repeat configurations during instance creation. In addition, image providers provide images that are pre-installed with various runtime environments and software applications in Alibaba Cloud Marketplace to suit different scenarios, such as website building, application development, and visualized management. You can select Alibaba Cloud Marketplace images based on your business requirements.


System disks and data disks are attached to instances to provide storage capacity. System disks contain images that are used to boot instances. Each instance must have a system disk. The first time an instance starts, the OS is installed and configurations are initialized based on the image that is stored on the system disk.

Cloud disks can be used as system disks or data disks. Local disks can be used only as data disks and are available only for specific instance types, such as big data instance types and instance types with local SSDs. If you want more storage space for your instance, you can extend the cloud disks on the instance or attach additional cloud disks to the instance after the instance is created. For more information, see Overview and Attach a data disk.

Business data is an important asset. Cloud disks adopt a triplicate mechanism to ensure data durability. To ensure data availability, we recommend that you back up data on a regular basis. You can create snapshots of cloud disks to back up disk data. If you use local disks, implement data redundancy at the application layer to ensure data availability.

In addition to the preceding basic configurations, you can specify custom network configurations, security groups, OS configurations, and grouping configurations for instances. For more information, see Create an instance by using the wizard.

Instance purchasing options

ECS provides a variety of instance purchasing options. You can select a purchasing option based on your business requirements. Examples:

  • To obtain consistent computing power, purchase subscription instances.

  • To meet dynamic computing power requirements, purchase pay-as-you-go instances.

  • To meet the computing power requirements of stateless applications and reduce compute costs, purchase preemptible instances.

  • To obtain both instance flexibility and cost savings, use pay-as-you-go instances together with reserved instances or savings plans.

  • To gain guaranteed access to compute resources, use pay-as-you-go instances together with resource reservations.

For information about other purchasing options, see Billing overview.

Usage instructions

Security suggestions

When you use cloud services, we recommend that you follow security suggestions to improve the security of cloud resources. Examples:

  • Suggestions for permission control: Use Resource Access Management (RAM) features to control which users can manage resources, such as instances, and what permissions to grant to the users.

  • Suggestions for security features: Use security features, such as security hardening and cloud disk encryption, to secure data and runtime environments.

  • Suggestions for network security: Use virtual private clouds (VPCs) to isolate services of different security levels. Use security groups to control inbound and outbound traffic for instances and allow instances to access the Internet only when necessary to minimize the attack surface area for resources.

For more information about how to improve the security of instances, see Best security practices.