An ECS instance is a virtual machine that contains basic computing components such as the vCPU, memory, operating system, network, and disk. You can fully customize and modify all configurations of an ECS instance. After you log on to the Alibaba Cloud Management console, you can manage resources and configure the environment of your ECS instances.
ECS instances are categorized into different instance families based on business scenarios. An instance family contains different instance types based on their vCPU and memory specifications. Instance types can have different vCPU and memory specifications, such as the CPU model and clock speed. Some software or applications require instance types that use specific vCPU and memory specifications. For example, if you want to use a Windows Server image, you must purchase an instance type that is equipped with a memory of at least 512 MiB. A vCPU stands for a thread. A CPU can run multiple threads.
For more information about instance types, see Instance families and Phased-out instance types. If the instance specifications cannot meet your application requirements, you can change the instance type. For more information, see Overview of instance upgrade and downgrade.
An ECS instance must contain a system disk to store the operating system and core configurations. An image is used to initialize a system disk and determines the operating system and initial software configurations of an ECS instance. Typically, the capacity of system disks is small. If you need more storage types or space, you can add data disks. For more information, see Block Storage overview.
ECS instances support the classic network and Virtual Private Cloud (VPC). We recommend that you use VPC. ECS instances in the same network, such as in the same VPC, can communicate over the internal network through private IP addresses. If you want your instances to communicate over the Internet, you can obtain the public IP addresses to communicate with devices on the Internet. For more information, see Network types.
For more information about the billing methods and prices of ECS instances, see Billing overview.