A deployment set is a policy that controls the distribution of ECS instances and implements disaster recovery and business availability when ECS instances are created.

Deployment policy

You can use a deployment set to distribute your ECS instances to different physical servers to guarantee high availability and set up underlying disaster recovery. When you create ECS instances in a deployment set, Alibaba Cloud will start the ECS instances on different physical servers within the specified region based on the deployment policy that you configured.

Deployment sets support the high availability policy:

  • When you use the high availability policy, all the ECS instances within your deployment set are strictly distributed across different physical servers within the specified region. The high availability policy applies to application architectures where several ECS instances must be isolated from each other. The policy significantly reduces the chances of service being unavailable.
  • When you use the high availability policy, you may not be able to create an ECS instance when there is a supply shortage in the specified region. Furthermore, pay-as-you-go instances in the No Fees for Stopped Instances (VPC-Connected) state may fail to start next time. If this problem occurs, we recommend that you wait a while and then try again or create a new instance.

Deployment example

The following figure shows a typical example on how to use a deployment set to improve business reliability. In the deployment set, four ECS instances are distributed to four different physical servers.Deployment set overview

If you want to achieve low-latency communication between ECS instances, we recommend that you make sure the network types of the instances are the same. For example, select the same VPC for the ECS instances when you create them.

Billing details

Deployment sets are free of charge, but you will be charged for the usage of ECS instances, disks, snapshots, images, and public bandwidth in deployment sets. For more information, see Billing overview.

Limits

Before you use deployment sets, note that:

  • Deployment sets cannot be merged.
  • You cannot create preemptible instances in deployment sets.
  • You cannot create dedicated hosts in deployment sets.
  • When you create ECS instances in a deployment set, you can create up to seven ECS instances in each zone. This limit varies with your ECS usage. You can use the following formula to calculate the number of ECS instances that can be created in an Alibaba Cloud region: 7 × Number of zones.
  • Instances in the following instance families can be created in deployment sets: c6, g6, r6, hfc6, hfg6, hfr6, d2, d2s, d2c, c5, d1, d1ne, g5, hfc5, hfg5, i2, i2g, i1, ic5, r5, se1ne, sn1ne, and sn2ne. For more information about instance types and their performance, see Instance families.
  • Supply shortage may result in a failure to create an instance or restart a pay-as-you-go instance that is in the No Fees for Stopped Instances (VPC-Connected) state in a deployment set. For more information, see No Fees for Stopped Instances (VPC-Connected).

For more information about the limits and quotas of deployment sets, see the "Deployment set limits" section in Limits.

References

API operations