This topic describes the information that you must know when you purchase ECS instances.

Resource upgrades

For information about how to upgrade ECS instances, see Overview of instance upgrade and downgrade. Before you upgrade ECS instances, take note of the following items:
  • With the exception of ECS instances that use local storage, ECS instances allow their CPU and memory resources to be scaled and their bandwidths to be upgraded while the instances are running. You can also downgrade ECS instances based on your business needs.
  • A maximum of 16 data disks can be attached to each ECS instance. You cannot reduce the size of a data disk after it has been extended.
  • The bandwidth of each ECS instance is measured in Mbit/s and ranges from 0 to 200 Mbit/s. You can temporarily upgrade the bandwidth of an ECS instance, or downgrade the instance when you renew it.


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