Host Aggregate : 用來在availability zone中進行劃分

Host aggregates are a mechanism to further partition an availability zone; while availability zones are visible to users, host aggregates are only visible to administrators. 

[Note]

Each node can have multiple aggregates, each aggregate can have multiple key-value pairs, and the same key-value pair can be assigned to multiple aggregate.

Xenserver

當使用Xenserver當作hypervisor時，可以使用host-aggregate來管理Xenserver Resource Pool以支援Live migration。