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

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<section id="best-practices-primary-storage">
        <title>Best Practices for Primary Storage</title>
        <itemizedlist>
            <listitem><para>The speed of primary storage will impact guest performance. If possible, choose smaller, higher RPM drives or SSDs for primary storage.</para></listitem>
            <listitem><para>There are two ways CloudStack can leverage primary storage:</para>
            <para>Static: This is CloudStack's traditional way of handling storage. In this model, a preallocated amount of storage (ex. a volume from a SAN) is given to CloudStack. CloudStack then permits many of its volumes to be created on this storage (can be root and/or data disks). If using this technique, ensure that nothing is stored on the storage. Adding the storage to &PRODUCT; will destroy any existing data.</para>
            <para>Dynamic: This is a newer way for CloudStack to manage storage. In this model, a storage system (rather than a preallocated amount of storage) is given to CloudStack. CloudStack, working in concert with a storage plug-in, dynamically creates volumes on the storage system and each volume on the storage system maps to a single CloudStack volume. This is highly useful for features such as storage Quality of Service. Currently this feature is supported for data disks (Disk Offerings).</para></listitem>
        </itemizedlist>
    </section>