Alibaba Cloud CDN nodes (also called points of presence, or PoPs) and mirrors both serve content to users, but they differ in how they store and retrieve that content.
Key differences
| CDN node (PoP) | Mirror | |
|---|---|---|
| What it stores | Cached copies of requested resources only | A complete replica of the entire website |
| How content is retrieved | Pulls from the origin server on first request (*Origin Pull*), then serves from cache | Serves directly from its own full copy — no origin server request needed |
| Who triggers retrieval | User requests trigger origin pulls | No user-triggered retrieval |
| Number of copies | Cached resources distributed across PoPs | Multiple full mirrors of the same site |
How a CDN node works
When a user requests a resource from an accelerated domain name:
CDN routes the request to the PoP nearest to the user.
The PoP checks its cache for the resource.
Cache hit: The PoP returns the cached resource directly to the user.
Cache miss: The PoP fetches the resource from the origin server (*Origin Pull*), caches it, and returns it to the user simultaneously.
Subsequent requests for the same resource are served from the cache — no origin pull required.
A CDN node stores only the resources that users have requested. It is not a full copy of your website.
How a mirror works
A mirror is a complete replica of a website. When users request resources, the mirror serves them directly from its own copy — no origin server request is needed. You can create multiple mirrors of the same website to distribute load or improve availability in specific regions.