mirror of https://github.com/tLDP/LDP
134 lines
4.3 KiB
XML
134 lines
4.3 KiB
XML
<appendix id="appxcsm"><title>The CSM plug-in</title>
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<para>The Cluster Segment Manager (CSM) is the EVMS plug-in that identifies and
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manages cluster storage. The CSM protects disk storage objects by writing metadata
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at the start and end of the disk, which prevents other plug-ins from attempting to use the disk.
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Other plug-ins can look at the disk, but they cannot see their own metadata signatures
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and cannot consume the disk. The protection that CSM provides allows the CSM to
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discover cluster storage and present it in an appropriate fashion to the system. </para>
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<para>All cluster storage disk objects must be placed in containers that have the
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following attributes:</para>
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<itemizedlist>
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<listitem>
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<para>cluster ID that identifies the cluster management software
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</para>
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</listitem>
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<listitem>
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<para>node ID that identifies the owner of the disk objects
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</para>
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</listitem>
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<listitem>
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<para>storage type: private, shared, or deported
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</para>
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</listitem>
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</itemizedlist>
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<para>
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The CSM plug-in reads metadata and constructs containers that consume
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the disk object. Each disk provides a usable area, mapped as an EVMS
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data segment, but only if the disk is accessible to the node viewing
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the storage.</para>
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<para>The CSM plug-in performs these operations:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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examines disk objects
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</para>
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</listitem>
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<listitem>
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<para>
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creates containers
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</para>
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</listitem>
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<listitem>
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<para>
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uses the containers to consume disk objects
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</para>
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</listitem>
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<listitem>
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<para>
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produces data segment objects if the disk is accessible to the node
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</para>
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</listitem>
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</itemizedlist>
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<sect1 id="csmassn"><title>Assigning the CSM plug-in</title>
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<para>Assigning a segment manager to a disk means that you want the plug-in to
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manage partitions on the disk. In order to do this, the plug-in needs to create and
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maintain appropriate metadata. The CSM creates the follow three segments on the disk:</para>
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<itemizedlist>
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<listitem>
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<para>primary metadata segment</para>
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</listitem>
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<listitem>
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<para>usable area data segment</para>
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</listitem>
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<listitem>
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<para>secondary metadata segment</para>
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</listitem>
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</itemizedlist>
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<para>The CSM collects the information it needs to perform the assign operation with the
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following options:</para>
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<variablelist>
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<varlistentry><term>NodeId</term>
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<listitem><para>Choose only from a list of configured node IDs that have been
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provided to the CSM by clustering software. The default selection is the
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node from which you are running the EVMS user interface.</para></listitem>
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</varlistentry>
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<varlistentry><term>Container Name</term>
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<listitem><para>The name for the container. You need to keep this name unique
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across the cluster to prevent name-in-conflict errors should the container fail over to
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another node that has a container with the same name.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry><term>Storage Type</term>
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<listitem><para>Can be either: share, private, or deported. </para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>Note that you would typically assign the CSM to a disk when you want to
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add a disk to an existing CSM container. If you are creating a new container, you
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have a choice of using either:
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<menuchoice>
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<guimenu>Actions</guimenu><guimenuitem>Create</guimenuitem><guimenuitem>Container</guimenuitem>
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</menuchoice> or
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<menuchoice><guimenu>Actions</guimenu><guimenuitem>Add</guimenuitem><guimenuitem>Segment Manager</guimenuitem></menuchoice>.
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</para>
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<para>If the container doesn't exist, it will be created for the disk. If the container already
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exists, the disk will be added to it.</para>
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</sect1>
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<sect1 id="unassignCSM"><title>Unassigning the CSM plug-in</title>
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<para>Unassigning a CSM plug-in results in the CSM removing its metadata from
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the specified disk storage object. The result is that the disk has no segments
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mapped and appears as a raw disk object. The disk is removed from the
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container that consumed it and the data segment is removed as well.</para>
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</sect1>
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<sect1><title>Deleting a CSM container</title>
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<para>An existing CSM container cannot be deleted if it is producing any data segments,
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because other EVMS plug-ins might be building higher-level objects on the CSM objects.
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To delete a CSM container, first remove disk objects from the container. When the last
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disk is removed, the container is also removed.</para>
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</sect1>
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</appendix>
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