libvirt/tests/storagevolxml2xmlin/vol-qcow2-clusterSize.xml

<volume>
  <name>OtherDemo.img</name>
  <key>/var/lib/libvirt/images/OtherDemo.img</key>
  <capacity unit="G">5</capacity>
  <allocation>294912</allocation>
  <target>
    <path>/var/lib/libvirt/images/OtherDemo.img</path>
    <format type='qcow2'/>
    <permissions>
      <mode>0644</mode>
      <owner>0</owner>
      <group>0</group>
      <label>unconfined_u:object_r:virt_image_t:s0</label>
    </permissions>
    <clusterSize unit='KiB'>128</clusterSize>
    <features>
      <extended_l2/>
    </features>
  </target>
</volume>
storage: add support for QCOW2 cluster_size option The default value hard-coded in QEMU (64KiB) is not always the ideal. Having a possibility to set the cluster_size by user may in specific use-cases improve performance for QCOW2 images. QEMU internally has some limits, the value has to be between 512B and 2048KiB and must by power of two, except when the image has Extended L2 Entries the minimal value has to be 16KiB. Since qemu-img ensures the value is correct and the limit is not always the same libvirt will not duplicate any of these checks as the error message from qemu-img is good enough: Cluster size must be a power of two between 512 and 2048k Resolves: https://gitlab.com/libvirt/libvirt/-/issues/154 Signed-off-by: Pavel Hrdina <phrdina@redhat.com> Reviewed-by: Peter Krempa <pkrempa@redhat.com> 2021-05-12 15:43:36 +00:00			`<volume>`
			`<name>OtherDemo.img</name>`
			`<key>/var/lib/libvirt/images/OtherDemo.img</key>`
			`<capacity unit="G">5</capacity>`
			`<allocation>294912</allocation>`
			`<target>`
			`<path>/var/lib/libvirt/images/OtherDemo.img</path>`
			`<format type='qcow2'/>`
			`<permissions>`
			`<mode>0644</mode>`
			`<owner>0</owner>`
			`<group>0</group>`
			`<label>unconfined_u:object_r:virt_image_t:s0</label>`
			`</permissions>`
			`<clusterSize unit='KiB'>128</clusterSize>`
storage: Introduce 'extended_l2' feature for storage volume QCOW2 images now support 'extended_l2' which splits the default clusters into 32 subcluster allocation units. This allows the allocation units to be smaller without increasing the size of L2 table too much and thus also the cache requirements for holding the full L2 table in memory. Unfortunately it's incompatible with qemu versions older than 5.2 thus can't be used as default. Signed-off-by: Peter Krempa <pkrempa@redhat.com> Reviewed-by: Ján Tomko <jtomko@redhat.com> 2021-12-14 15:05:09 +00:00			`<features>`
			`<extended_l2/>`
			`</features>`
storage: add support for QCOW2 cluster_size option The default value hard-coded in QEMU (64KiB) is not always the ideal. Having a possibility to set the cluster_size by user may in specific use-cases improve performance for QCOW2 images. QEMU internally has some limits, the value has to be between 512B and 2048KiB and must by power of two, except when the image has Extended L2 Entries the minimal value has to be 16KiB. Since qemu-img ensures the value is correct and the limit is not always the same libvirt will not duplicate any of these checks as the error message from qemu-img is good enough: Cluster size must be a power of two between 512 and 2048k Resolves: https://gitlab.com/libvirt/libvirt/-/issues/154 Signed-off-by: Pavel Hrdina <phrdina@redhat.com> Reviewed-by: Peter Krempa <pkrempa@redhat.com> 2021-05-12 15:43:36 +00:00			`</target>`
			`</volume>`