188 lines
9.2 KiB
XML
188 lines
9.2 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>The 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>This driver enables the use of GPFS in a similar fashion
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as 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 Cinder volume and Nova compute
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services are running 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 GPFS Administration documentation.</para>
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</note>
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</para>
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<para>Optionally, Glance can be configured to store images on
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a GPFS file system. When Cinder volumes are created from
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Glance images, if both image and volume data reside in the
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same GPFS file system, the data from image files is moved
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efficiently to Cinder volumes 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>Enabling the GPFS Driver</title>
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<para>To use Cinder 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.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-gpfs_volume.xml"/>
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<note>
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<para>The flag <literal>gpfs_images_share_mode</literal>
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is only valid if the Image service is configured to
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use GPFS with <literal>gpfs_images_dir</literal> flag.
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Also note, 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 flags
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<literal>gpfs_mount_point_base</literal> and
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<literal>gpfs_images_dir</literal> 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>The driver will create a file system or 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 type, for example
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ext3, ext4, etc.</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>The driver will set the file system label for
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the file system specified by fstype option.
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This value is only used if fstype 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>The driver will assign the volume file
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to the specified GPFS storage pool. Note
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that the GPFS storage pool must already be
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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>Specify 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 MaxDataReplicas 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>Enable or disable the Direct I/O caching
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policy for the volume file. Valid values
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are "yes" and "no".</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>Specify the allocation policy to be used
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for the volume file. Note that this option
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only works if "allow-write-affinity" 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>Specify how many blocks are laid out
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sequentially in the volume file to behave
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like a single large block. This option
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only works if "allow-write-affinity" 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>Specify 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 GPFS Administration and
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Programming Reference guide 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 Using Volume Creation Options</title>
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<para>This example shows the creation of a 50GB volume
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with an ext4 filesystem labeled
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<literal>newfs</literal>and direct IO
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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
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snapshot or from an existing volume, the same approach
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is taken. The same approach is also used when a new
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volume is created from a Glance image, if the source
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image is in raw format, and
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<literal>gpfs_images_share_mode</literal> is set
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to <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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