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<title>Lustre Recovery</title>
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- <entry align="left"><para>Lustre 2.0 Operations Manual</para></entry>
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- <entry align="right"><para><anchor xml:id="dbdoclet.50438268_pgfId-874" xreflabel=""/>C H A P T E R 30<anchor xml:id="dbdoclet.50438268_71884" xreflabel=""/></para></entry>
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- <entry align="right"><para><anchor xml:id="dbdoclet.50438268_pgfId-5529" xreflabel=""/><anchor xml:id="dbdoclet.50438268_93053" xreflabel=""/>Lustre Recovery</para></entry>
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<para><anchor xml:id="dbdoclet.50438268_pgfId-1292351" xreflabel=""/>This chapter describes how recovery is implemented in Lustre and includes the following sections:</para>
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<para><anchor xml:id="dbdoclet.50438268_pgfId-1287370" xreflabel=""/><link xl:href="LustreRecovery.html#50438268_58047">Recovery Overview</link></para>
<para><anchor xml:id="dbdoclet.50438268_pgfId-1287894" xreflabel=""/>In pre-VBR versions of Lustre, if the MGS or an OST went down and then recovered, a recovery process was triggered in which clients attempted to replay their requests. Clients were only allowed to replay RPCs in serial order. If a particular client could not replay its requests, then those requests were lost as well as the requests of clients later in the sequence. The ''downstream'' clients never got to replay their requests because of the wait on the earlier client’s RPCs. Eventually, the recovery period would time out (so the component could accept new requests), leaving some number of clients evicted and their requests and data lost.</para>
<para><anchor xml:id="dbdoclet.50438268_pgfId-1287896" xreflabel=""/>With VBR, the recovery mechanism does not result in the loss of clients or their data, because changes in inode versions are tracked, and more clients are able to reintegrate into the cluster. With VBR, inode tracking looks like this:</para>
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- <para><anchor xml:id="dbdoclet.50438268_pgfId-1288169" xreflabel=""/> Each inode<anchor xml:id="fnote2" xreflabel=""/><link linkend="dbdoclet.50438268_pgfId-1288489"><superscript>[2]</superscript></link> stores a version, that is, the number of the last transaction (transno) in which the inode was changed.</para>
+ <para><anchor xml:id="dbdoclet.50438268_pgfId-1288169" xreflabel=""/> Each inode<footnote><para><anchor xml:id="dbdoclet.50438268_pgfId-1288489" xreflabel=""/>Usually, there are two inodes, a parent and a child.</para></footnote> stores a version, that is, the number of the last transaction (transno) in which the inode was changed.</para>
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- <!--para><emphasis role="bold"><superscript>1<link linkend="fnote1">(Footnote)</link><anchor xml:id="dbdoclet.50438268_pgfId-1288438" xreflabel=""/>There are two scenarios under which client RPCs are not replayed: (1) Non-functioning or isolated clients do not reconnect, and they cannot replay their RPCs, causing a gap in the replay sequence. These clients get errors and are evicted. (2) Functioning clients connect, but they cannot replay some or all of their RPCs that occurred after the gap caused by the non-functioning/isolated clients. These clients get errors (caused by the failed clients). With VBR, these requests have a better chance to replay because the "gaps" are only related to specific files that the missing client(s) changed.</superscript></emphasis></para-->
- <para><emphasis role="bold"><superscript>2<link linkend="fnote2">(Footnote)</link><anchor xml:id="dbdoclet.50438268_pgfId-1288489" xreflabel=""/>Usually, there are two inodes, a parent and a child.</superscript></emphasis></para>
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- <entry align="left"><para>Lustre 2.0 Operations Manual</para></entry>
- <entry align="right"><para>821-2076-10</para></entry>
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- <para><link xl:href="copyright.html">Copyright</link> © 2011, Oracle and/or its affiliates. All rights reserved.</para>
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