Last updated: 2019-07-25 17:30:00PDF
You can launch instances in a placement group which determines how the instances are placed on the underlying hardware. When creating a placement group, you can distribute the instances in the group to different underlying hardware.
This feature is under internal trial.
Spread Placement Groups
A spread placement group contains a set of instances that are placed on different underlying hardware.
For applications of important instances that need to be placed separately, such as master/slave databases and high-availability clusters, a spread placement group is recommended. By launching instances in a spread placement group, you can reduce the risk of simultaneous failure that occurs when the instances are placed on the same underlying hardware.
A spread placement group has geographical attributes and can be deployed across multiple availability zones. There is a limit on the number of instances in a group. For more information, please see the Console page on the official website.
When you launch instances in a spread placement group, the request may fail in case of insufficient hardware. We provide more different hardware so that you can retry your request.
Spread Placement Group Rules and Limits
Before using a spread placement group, you should pay attention to the following rules:
- Placement groups cannot be merged.
- An instance can be launched in a placement group at a time.
- An instance cannot be placed across multiple placement groups.
- Existing instances cannot be automatically added into a placement group.
- Spread placement layers can be selected, including physical machine, exchange, and rack.
- The maximum numbers of instances in groups on different placement layers are different. For more information, please see the official website.
- The disaster recovery group policy you have specified is strictly complied with. Please note that if there is not enough hardware to distribute instances, the creation of some instances will fail.
- Instances on CDH don't support spread placement groups.
For more information on how to work with spread placement groups, please see Spread Placement Group.