LUDOC-317 proc: OST reserved size

Clarify how a MDT use a OST for object allocation base on
reserved space. LU-6910 adds configurable values
reserved_mb_{low|high}. And this patch adds desciption for them.

Signed-off-by: Alexander Boyko <alexander.boyko@seagate.com>
Change-Id: I3e7787781b30c6c6df0dde9661e369254242fc5b
Reviewed-on: http://review.whamcloud.com/17560
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>

diff --git a/LustreProc.xml b/LustreProc.xml
index 511b2b3..bcdf708 100644 (file)
--- a/LustreProc.xml
+++ b/LustreProc.xml
@@ -2174,6 +2174,16 @@ nid                    refs   peer    max   tx    min
           value is 91 percent. When the free space priority is set to 100, weighting is based
           entirely on free space and location is no longer used by the striping algorthm.</para>
       </listitem>
+      <listitem>
+        <para condition="l29"><literal>reserved_mb_low</literal> - The low watermark used to stop
+          object allocation if available space is less than it. The default is 0.1 percent of total
+          OST size.</para>
+      </listitem>
+       <listitem>
+        <para condition="l29"><literal>reserved_mb_high</literal> - The high watermark used to start
+          object allocation if available space is more than it. The default is 0.2 percent of total
+          OST size.</para>
+      </listitem>
     </itemizedlist>
     <para>For more information about monitoring and managing free space, see <xref
         xmlns:xlink="http://www.w3.org/1999/xlink" linkend="dbdoclet.50438209_10424"/>.</para>

diff --git a/ManagingStripingFreeSpace.xml b/ManagingStripingFreeSpace.xml
index c07c82e..7031bb4 100644 (file)
--- a/ManagingStripingFreeSpace.xml
+++ b/ManagingStripingFreeSpace.xml
@@ -381,7 +381,16 @@ osc.lustre-OST0002-osc.ost_conn_uuid=192.168.20.1@tcp</screen></para>
       preference to location (spreading out stripes across OSSs to increase network bandwidth
       utilization) and the weighted allocator gives preference to available space (balancing loads
       across OSTs). Threshold and weighting factors for these two algorithms can be adjusted by the
-      user. This section describes how to check available free space on disks and how free space is
+      user. The MDT reserves 0.1 percent of total OST space and 32 inodes for each OST. The MDT
+      stops object allocation for the OST if available space is less than reserved or the OST has
+      fewer than 32 free inodes. The MDT starts object allocation when available space is twice
+      as big as the reserved space and the OST has more than 64 free inodes. Note, clients
+      could appened existing files no matter what object allocation state is.</para>
+    <para condition="l29"> The reserved space for each OST can be adjusted by the user. Use the
+      <literal>lctl set_param</literal> command, for example the next command reserve 1GB space
+      for all OSTs.
+      <screen>lctl set_param -P osp.*.reserved_mb_low=1024</screen></para>
+    <para>This section describes how to check available free space on disks and how free space is
       allocated. It then describes how to set the threshold and weighting factors for the allocation
       algorithms.</para>
     <section xml:id="dbdoclet.50438209_35838">