This topic describes the information that you must understand before you purchase Elastic Compute Service (ECS) instances.

Resource upgrades

For information about how to upgrade the configurations of ECS instances, see Overview of instance upgrade and downgrade. Before you upgrade the configurations of ECS instances, take note of the following items:
  • Except ECS instances that use local storage, ECS instances can have their CPU and memory resources scaled and their bandwidths upgraded while the instances are running. You can also downgrade the configurations of ECS instances.
  • Typically, a maximum of 16 data disks can be attached to each ECS instance. You cannot reduce the size of a data disk after the data disk is extended.
  • The bandwidth of each ECS instance is measured in Mbit/s and can range from 0 Mbit/s to 200 Mbit/s. You can modify the bandwidth or change the billing method for network usage.


The following topics describe the basic terms of ECS and how to use ECS:
  • For information about the terms and services related to ECS, see What is ECS?
  • For information about how to choose ECS instance families, see Instance families.
  • For information about how to choose images, see Select an image.
  • For information about the performance of Elastic Block Storage devices, see EBS performance.
  • For information about the usage considerations of ECS instances, see Usage notes.
  • For information about the features of pay-as-you-go resources, see Pay-as-you-go.
  • For information about the features of subscription resources, see Subscription.
  • For information about the limits that apply to ECS, see Limits.
  • If you want to select instance types based on their benchmark data for compute performance, contact the Service Manager or Submit a ticket to contact Alibaba Cloud after-sales support.