<mirrors>
    <!-- mirror
     | Specifies a repository mirror site to use instead of a given repository. The repository that
     | this mirror serves has an ID that matches the mirrorOf element of this mirror. IDs are used
     | for inheritance and direct lookup purposes, and must be unique across the set of mirrors.
     |
    <mirror>
      <id>mirrorId</id>
      <mirrorOf>repositoryId</mirrorOf>
      <name>Human Readable Name for this Mirror.</name>
      <url>http://my.repository.com/repo/path</url>
    </mirror>
     -->
    <mirror>
        <id>nexus-osc</id>
        <mirrorOf>central</mirrorOf>
        <name>Nexus osc</name>
        <url>http://maven.oschina.net/content/groups/public/</url>
    </mirror>
    <mirror>
        <id>nexus-osc-thirdparty</id>
        <mirrorOf>thirdparty</mirrorOf>
        <name>Nexus osc thirdparty</name>
        <url>http://maven.oschina.net/content/repositories/thirdparty/</url>
    </mirror>
    <mirror>
        <id>maven2</id>
        <mirrorOf>maven2</mirrorOf>
        <name>maven2</name>
        <url>http://repo1.maven.org/maven2/</url>
    </mirror>
</mirrors>

Qual é exatamente o uso demirrorOf? O maven tentará primeiro obter o frasco deid=nexus-osc e depoisnexus-osc-thirdparty e depoismaven2? Eu já verifiquei oguia de configuração do espelho maven mas eu ainda não consigo entender.