186 lines
8.4 KiB
XML
186 lines
8.4 KiB
XML
<section xml:id="GPFS-driver" xmlns="http://docbook.org/ns/docbook"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0">
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<title>IBM GPFS volume driver</title>
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<para>IBM General Parallel File System (GPFS) is a cluster file
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system that provides concurrent access to file systems from
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multiple nodes. The storage provided by these nodes can be
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direct attached, network attached, SAN attached, or a
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combination of these methods. GPFS provides many features
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beyond common data access, including data replication, policy
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based storage management, and space efficient file snapshot
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and clone operations.</para>
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<section xml:id="GPFS-driver-background">
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<title>How the GPFS driver works</title>
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<para>The GPFS driver enables the use of GPFS in a fashion
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similar to that of the NFS driver. With the GPFS driver, instances do not
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actually access a storage device at the block level.
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Instead, volume backing files are created in a GPFS file
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system and mapped to instances, which emulate a block
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device.</para>
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<para>
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<note>
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<para>GPFS software must be installed and running on
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nodes where Block Storage and Compute
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services run in the OpenStack environment.
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A GPFS file system must also be created and
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mounted on these nodes before starting the
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<literal>cinder-volume</literal> service. The
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details of these GPFS specific steps are covered
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in <citetitle>GPFS: Concepts, Planning, and Installation Guide</citetitle>
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and <citetitle>GPFS: Administration and Programming Reference</citetitle>.
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</para>
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</note>
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</para>
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<para>Optionally, the Image Service can be configured to store images on
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a GPFS file system. When a Block Storage volume is created from
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an image, if both image data and volume data reside in the
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same GPFS file system, the data from image file is moved
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efficiently to the volume file using copy-on-write
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optimization strategy.</para>
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</section>
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<section xml:id="GPFS-driver-options">
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<title>Enable the GPFS driver</title>
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<para>To use the Block Storage service with the GPFS driver, first set the
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<literal>volume_driver</literal> in
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<filename>cinder.conf</filename>:</para>
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<programlisting>volume_driver = cinder.volume.drivers.ibm.gpfs.GPFSDriver</programlisting>
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<para>The following table contains the configuration options
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supported by the GPFS driver.</para>
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<xi:include
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href="../../../common/tables/cinder-storage_gpfs.xml"/>
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<note>
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<para>The <literal>gpfs_images_share_mode</literal>
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flag is only valid if the Image Service is configured to
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use GPFS with the <literal>gpfs_images_dir</literal> flag.
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When the value of this flag is
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<literal>copy_on_write</literal>, the paths
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specified by the
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<literal>gpfs_mount_point_base</literal> and
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<literal>gpfs_images_dir</literal> flags must both
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reside in the same GPFS file system and in the same
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GPFS file set.</para>
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</note>
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</section>
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<section xml:id="GPFS-volume-options">
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<title>Volume creation options</title>
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<para>It is possible to specify additional volume
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configuration options on a per-volume basis by specifying
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volume metadata. The volume is created using the specified
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options. Changing the metadata after the volume is created
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has no effect. The following table lists the volume
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creation options supported by the GPFS volume
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driver.</para>
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<table rules="all">
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<caption>Volume Create Options for GPFS Volume
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Drive</caption>
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<thead>
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<tr>
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<th>Metadata Item Name</th>
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<th>Description</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td><literal>fstype</literal></td>
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<td>Specifies whether to create a file system or a swap
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area on the new volume. If
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<literal>fstype=swap</literal> is
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specified, the mkswap command is used to
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create a swap area. Otherwise the mkfs command
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is passed the specified file system type, for example
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ext3, ext4 or ntfs.</td>
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</tr>
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<tr>
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<td><literal>fslabel</literal></td>
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<td>Sets the file system label for
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the file system specified by <literal>fstype</literal> option.
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This value is only used if <literal>fstype</literal> is
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specified.</td>
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</tr>
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<tr>
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<td><literal>data_pool_name</literal></td>
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<td>
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<para>Specifies the GPFS storage pool to which the volume is to be assigned.
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Note: The GPFS storage pool must already have been
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created.</para>
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</td>
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</tr>
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<tr>
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<td><literal>replicas</literal></td>
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<td>
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<para>Specifies how many copies of the volume
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file to create. Valid values are 1, 2,
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and, for GPFS V3.5.0.7 and later, 3. This
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value cannot be greater than the value of
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the <literal>MaxDataReplicas</literal> attribute of the file
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system.</para>
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</td>
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</tr>
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<tr>
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<td><literal>dio</literal></td>
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<td>
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<para>Enables or disables the Direct I/O caching
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policy for the volume file. Valid values
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are <literal>yes</literal> and <literal>no</literal>.</para>
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</td>
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</tr>
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<tr>
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<td><literal>write_affinity_depth</literal></td>
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<td>
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<para>Specifies the allocation policy to be used
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for the volume file. Note: This option
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only works if <literal>allow-write-affinity</literal> is
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set for the GPFS data pool.</para>
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</td>
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</tr>
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<tr>
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<td><literal>block_group_factor</literal></td>
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<td>
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<para>Specifies how many blocks are laid out
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sequentially in the volume file to behave
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as a single large block. Note: This option
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only works if <literal>allow-write-affinity</literal> is
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set for the GPFS data pool.</para>
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</td>
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</tr>
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<tr>
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<td><literal>write_affinity_failure_group</literal></td>
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<td>
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<para>Specifies the range of nodes (in GPFS
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shared nothing architecture) where
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replicas of blocks in the volume file are
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to be written. See <citetitle>GPFS: Administration and
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Programming Reference</citetitle> for more
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details on this option.</para>
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</td>
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</tr>
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</tbody>
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</table>
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<simplesect>
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<title>Example: Volume creation options</title>
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<para>This example shows the creation of a 50GB volume with an <systemitem>ext4</systemitem>
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file system labeled <literal>newfs</literal> and direct IO enabled:</para>
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<screen><prompt>$</prompt> <userinput>cinder create --metadata fstype=ext4 fslabel=newfs dio=yes --display-name volume_1 50</userinput> </screen>
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</simplesect>
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</section>
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<section xml:id="GPFS-operational-notes">
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<title>Operational notes for GPFS driver</title>
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<simplesect>
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<title>Snapshots and clones</title>
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<para>Volume snapshots are implemented using the GPFS file
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clone feature. Whenever a new snapshot is created, the
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snapshot file is efficiently created as a read-only
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clone parent of the volume, and the volume file uses
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copy-on-write optimization strategy to minimize data
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movement.</para>
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<para>Similarly when a new volume is created from a snapshot or from an existing volume, the
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same approach is taken. The same approach is also used when a new volume is created
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from an Image Service image, if the source image is in raw format, and
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<literal>gpfs_images_share_mode</literal> is set to
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<literal>copy_on_write</literal>.</para>
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</simplesect>
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</section>
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</section>
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