Merge "Configure and use volume number weigher"

doc/admin-guide-cloud/blockstorage/section_volume_number_weighter.xml

@@ -0,0 +1,70 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE section [
+<!ENTITY % openstack SYSTEM "../../common/entities/openstack.ent">
+%openstack;
+]>
+<section xmlns="http://docbook.org/ns/docbook"
+  xmlns:xi="http://www.w3.org/2001/XInclude"
+  xmlns:xlink="http://www.w3.org/1999/xlink"
+  version="5.0"
+  xml:id="volume_number_weighter">
+    <title>Configure and use volume number weighter</title>
+    <para>OpenStack Block Storage enables you to choose a volume back end
+according
+    to <option>free_capacity</option> and <option>allocated_capacity</option>.
+    The volume number weighter feature lets the scheduler choose a volume back end based
+    on its volume number in the volume back end. This can provide another means to improve
+    the volume back ends' I/O balance and the volumes' I/O performance.</para>
+    <simplesect>
+        <title>Enable volume number weighter</title>
+        <para>To enable a volume number weighter, set the <option>scheduler_default_weighters</option>
+        to <literal>VolumeNumberWeigher</literal> flag in the <filename>cinder.conf</filename> file to
+        define <literal>VolumeNumberWeigher</literal> as the selected weighter.
+        </para>
+    </simplesect>
+    <simplesect>
+        <title>Configure multiple-storage back ends</title>
+        <para>To configure <literal>VolumeNumberWeigher</literal>, use <literal>LVMISCSIDriver</literal> as the volume driver.</para>
+        <para>This configuration defines two LVM volume groups: <literal>stack-volumes</literal> with 10&nbsp;GB capacity
+        and <literal>stack-volumes-1</literal> with 60&nbsp;GB capacity.
+        This example configuration defines two back ends:</para>
+        <programlisting language="ini">scheduler_default_weighers=VolumeNumberWeigher
+enabled_backends=lvmdriver-1,lvmdriver-2
+[lvmdriver-1]
+volume_group=stack-volumes
+volume_driver=cinder.volume.drivers.lvm.LVMISCSIDriver
+volume_backend_name=LVM_iSCSI
+
+[lvmdriver-2]
+volume_group=stack-volumes-1
+volume_driver=cinder.volume.drivers.lvm.LVMISCSIDriver
+volume_backend_name=LVM_iSCSI</programlisting>
+    </simplesect>
+        <simplesect>
+        <title>Volume type</title>
+        <para>Define a volume type in Block Storage:</para>
+        <screen><prompt>$</prompt> <userinput>cinder admin type-create lvm</userinput></screen>
+        <para>Create an extra specification that links
+            the volume type to a back-end name:</para>
+        <screen><prompt>$</prompt> <userinput>cinder type-key lvm set volume_backend_name=LVM_iSCSI</userinput></screen>
+        <para>This example creates a <literal>lvm</literal> volume
+            type with <literal>volume_backend_name=LVM_iSCSI</literal>
+            as extra specifications.</para>
+    </simplesect>
+    <simplesect>
+        <title>Usage</title>
+        <para>To create six 1-GB volumes, run the <command>cinder create --volume-type lvm 1</command> command
+six times:</para>
+            <screen><prompt>$</prompt> <userinput>cinder create --volume-type lvm 1</userinput></screen>
+             <para>This command creates three volumes in <literal>stack-volumes</literal> and three volumes in <literal>stack-volumes-1</literal>.</para>
+<para>List the available volumes:</para>
+<screen><prompt>#</prompt> <userinput>lvs</userinput>
+<computeroutput>  LV                                          VG              Attr      LSize  Pool Origin Data%  Move Log Copy%  Convert
+  volume-3814f055-5294-4796-b5e6-1b7816806e5d stack-volumes   -wi-a----  1.00g
+  volume-72cf5e79-99d2-4d23-b84e-1c35d3a293be stack-volumes   -wi-a----  1.00g
+  volume-96832554-0273-4e9d-902b-ad421dfb39d1 stack-volumes   -wi-a----  1.00g
+  volume-169386ef-3d3e-4a90-8439-58ceb46889d9 stack-volumes-1 -wi-a----  1.00g
+  volume-460b0bbb-d8a0-4bc3-9882-a129a5fe8652 stack-volumes-1 -wi-a----  1.00g
+  volume-9a08413b-0dbc-47c9-afb8-41032ab05a41 stack-volumes-1 -wi-a----  1.00g</computeroutput></screen>
+    </simplesect>
+</section>

doc/admin-guide-cloud/ch_blockstorage.xml

@@ -148,6 +148,7 @@
                 create, delete, and verify volumes and determine
                 targets and add iSCSI initiators to the system.</para>
         </section>
+        <xi:include href="blockstorage/section_volume_number_weighter.xml"/>
     </section>
     <section xml:id="troubleshooting-cinder-install">
         <title>Troubleshoot your installation</title>