docs/en-US/best-practices-secondary-storage.xml

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<section id="best-practices-secondary-storage">
        <title>Best Practices for Secondary Storage</title>
        <itemizedlist>
            <listitem><para>Each Zone can have one or more secondary storage servers. Multiple secondary storage servers provide increased scalability to the system.</para></listitem>
            <listitem><para>Secondary storage has a high read:write ratio and is expected to consist of larger drives with lower IOPS than primary storage.</para></listitem>
            <listitem><para>Ensure that nothing is stored on the server. Adding the server to &PRODUCT; will destroy any existing data.</para></listitem>            
        </itemizedlist>
    </section>