A content delivery network, CDN, comprising: a first-level CDN node that is formed of a first CDN media server and a first CDN content storage and is configured to provide content for a user; and a second-level CDN node that is formed of a second CDN media server and a second content storage and interconnects with the first-level CDN node, wherein: the first CDN media server mounts the logical storage unit in the second CDN content storage by using an IP-layer storage access protocol, generates a second content index corresponding to the logical storage unit in the second CDN content storage and accesses the content in the second CDN content storage by using an IP-layer storage access protocol, wherein the first CDN media server, by mounting a logical storage unit in the first CDN content storage, generates a first content index corresponding to the logical storage unit in the first CDN content storage, and wherein: when receiving, from a user, a request for accessing content, the first CDN media server searches the first content index and the second content index to obtain a CDN content storage where the requested access content is located; when the requested access content is stored in the first CND content storage, the first CDN media server obtains the requested access content from the first CDN content storage; and when the requested access content is stored in the second CDN content storage, the first CDN media server accesses the second CDN content storage by using the IP-layer storage access protocol to obtain the requested access content. a first-level CDN node that is formed of a first CDN media server and a first CDN content storage and is configured to provide content for a user; and a second-level CDN node that is formed of a second CDN media server and a second content storage and interconnects with the first-level CDN node, wherein: the first CDN media server mounts the logical storage unit in the second CDN content storage by using an IP-layer storage access protocol, generates a second content index corresponding to the logical storage unit in the second CDN content storage and accesses the content in the second CDN content storage by using an IP-layer storage access protocol, wherein the first CDN media server, by mounting a logical storage unit in the first CDN content storage, generates a first content index corresponding to the logical storage unit in the first CDN content storage, and wherein: when receiving, from a user, a request for accessing content, the first CDN media server searches the first content index and the second content index to obtain a CDN content storage where the requested access content is located; when the requested access content is stored in the first CND content storage, the first CDN media server obtains the requested access content from the first CDN content storage; and when the requested access content is stored in the second CDN content storage, the first CDN media server accesses the second CDN content storage by using the IP-layer storage access protocol to obtain the requested access content. the first CDN media server mounts the logical storage unit in the second CDN content storage by using an IP-layer storage access protocol, generates a second content index corresponding to the logical storage unit in the second CDN content storage and accesses the content in the second CDN content storage by using an IP-layer storage access protocol, wherein the first CDN media server, by mounting a logical storage unit in the first CDN content storage, generates a first content index corresponding to the logical storage unit in the first CDN content storage, and wherein: when receiving, from a user, a request for accessing content, the first CDN media server searches the first content index and the second content index to obtain a CDN content storage where the requested access content is located; when the requested access content is stored in the first CND content storage, the first CDN media server obtains the requested access content from the first CDN content storage; and when the requested access content is stored in the second CDN content storage, the first CDN media server accesses the second CDN content storage by using the IP-layer storage access protocol to obtain the requested access content. when receiving, from a user, a request for accessing content, the first CDN media server searches the first content index and the second content index to obtain a CDN content storage where the requested access content is located; when the requested access content is stored in the first CND content storage, the first CDN media server obtains the requested access content from the first CDN content storage; and when the requested access content is stored in the second CDN content storage, the first CDN media server accesses the second CDN content storage by using the IP-layer storage access protocol to obtain the requested access content.