LUDOC-504 nodemap: servers must be in a trusted+admin group

[doc/manual.git] / UnderstandingLustre.xml

diff --git a/UnderstandingLustre.xml b/UnderstandingLustre.xml
index 377b1d1..f8c6ff6 100644 (file)
--- a/UnderstandingLustre.xml
+++ b/UnderstandingLustre.xml
@@ -67,7 +67,7 @@
       <para>Lustre file systems run on a variety of vendor's kernels. For more
       details, see the Lustre Test Matrix
       <xref xmlns:xlink="http://www.w3.org/1999/xlink"
-      linkend="dbdoclet.50438261_99193" />.</para>
+       linkend="preparing_installation" />.</para>
       <para>A Lustre installation can be scaled up or down with respect to the
       number of client nodes, disk storage and bandwidth. Scalability and
       performance are dependent on available disk and network bandwidth and the
@@ -732,7 +732,7 @@
     <emphasis role="italic">striped</emphasis> across the objects using RAID 0,
     and each object is stored on a different OST. (For more information about
     how striping is implemented in a Lustre file system, see
-    <xref linkend="dbdoclet.50438250_89922" />.</para>
+    <xref linkend="lustre_striping" />.</para>
     <figure xml:id="Fig1.3_LayoutEAonMDT">
       <title>Layout EA on MDT pointing to file data on OSTs</title>
       <mediaobject>
@@ -791,7 +791,7 @@
         available space of all the OSTs.</para>
       </listitem>
     </itemizedlist>
-    <section xml:id="dbdoclet.50438250_89922">
+    <section xml:id="lustre_striping">
       <title>
       <indexterm>
         <primary>Lustre</primary>
@@ -810,7 +810,7 @@
       ability to stripe is also useful when a single OST does not have enough
       free space to hold an entire file. For more information about benefits
       and drawbacks of file striping, see
-      <xref linkend="dbdoclet.50438209_48033" />.</para>
+      <xref linkend="file_striping.considerations" />.</para>
       <para>Striping allows segments or 'chunks' of data in a file to be stored
       on different OSTs, as shown in
       <xref linkend="understandinglustre.fig.filestripe" />. In the Lustre file
@@ -830,7 +830,7 @@
       for
       <literal>stripe_size</literal> is 1MB. The user may change these values on
       a per directory or per file basis. For more details, see
-      <xref linkend="dbdoclet.50438209_78664" />.</para>
+      <xref linkend="file_striping.lfs_setstripe" />.</para>
       <para>
       <xref linkend="understandinglustre.fig.filestripe" />, the
       <literal>stripe_size</literal> for File C is larger than the
@@ -875,9 +875,46 @@
       to utilize the full file system bandwidth.</para>
       <para>For more information about striping, see
       <xref linkend="managingstripingfreespace" />.</para>
+      <para>
+        <emphasis role="bold">Extended Attributes(xattrs)</emphasis></para>
+         <para>Lustre uses lov_user_md_v1/lov_user_md_v3 data-structures to
+         maintain its file striping information under xattrs. Extended
+         attributes are created when files and directory are created. Lustre
+         uses <literal>trusted</literal> extended attributes to store its
+         parameters which are root-only accessible. The parameters are:</para>
+      <itemizedlist>
+        <listitem>
+          <para>
+            <emphasis role="bold"><literal>trusted.lov</literal>:</emphasis>
+            Holds layout for a regular file, or default file layout stored
+            on a directory (also accessible as <literal>lustre.lov</literal>
+            for non-root users).
+          </para>
+        </listitem>
+        <listitem>
+          <para>
+            <emphasis role="bold"><literal>trusted.lma</literal>:</emphasis>
+            Holds FID and extra state flags for current file</para>
+        </listitem>
+        <listitem>
+          <para>
+            <emphasis role="bold"><literal>trusted.lmv</literal>:</emphasis>
+            Holds layout for a striped directory (DNE 2), not present otherwise
+          </para>
+        </listitem>
+        <listitem>
+          <para>
+            <emphasis role="bold"><literal>trusted.link</literal>:</emphasis>
+            Holds parent directory FID + filename for each link to a file
+            (for <literal>lfs fid2path</literal>)</para>
+        </listitem>
+      </itemizedlist>
+      <para>xattr which are stored and present in the file could be verify
+        using:</para>
+      <para><screen># getfattr -d -m - /mnt/testfs/file></screen></para>
     </section>
   </section>
 </chapter>
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