Improve gpfs config flag help text readability

Modify the help text for gpfs configuration flags so that it
reads more clearly.

Closes-Bug: #1233288

Change-Id: Iea41bceb496dfaa1f8625a6e3abb31794838213d

cinder/volume/drivers/gpfs.py

@@ -40,32 +40,37 @@
 gpfs_opts = [
     cfg.StrOpt('gpfs_mount_point_base',
                default=None,
-               help='Path to the directory on GPFS mount point where '
-                    'volumes are stored'),
+               help='Specifies the path of the GPFS directory where Block '
+                    'Storage volume and snapshot files are stored.'),
     cfg.StrOpt('gpfs_images_dir',
                default=None,
-               help='Path to GPFS Glance repository as mounted on '
-                    'Nova nodes'),
+               help='Specifies the path of the Image service repository in '
+                    'GPFS.  Leave undefined if not storing images in GPFS.'),
     cfg.StrOpt('gpfs_images_share_mode',
                default=None,
-               help='Set this if Glance image repo is on GPFS as well '
-                    'so that the image bits can be transferred efficiently '
-                    'between Glance and Cinder.  Valid values are copy or '
-                    'copy_on_write. copy performs a full copy of the image, '
-                    'copy_on_write efficiently shares unmodified blocks of '
-                    'the image.'),
+               help='Specifies the type of image copy to be used.  Set this '
+                    'when the Image service repository also uses GPFS so '
+                    'that image files can be transferred efficiently from '
+                    'the Image service to the Block Storage service. There '
+                    'are two valid values: "copy" specifies that a full copy '
+                    'of the image is made; "copy_on_write" specifies that '
+                    'copy-on-write optimization strategy is used and '
+                    'unmodified blocks of the image file are shared '
+                    'efficiently.'),
     cfg.IntOpt('gpfs_max_clone_depth',
                default=0,
-               help='A lengthy chain of copy-on-write snapshots or clones '
-                    'could have impact on performance.  This option limits '
-                    'the number of indirections required to reach a specific '
-                    'block. 0 indicates unlimited.'),
+               help='Specifies an upper limit on the number of indirections '
+                    'required to reach a specific block due to snapshots or '
+                    'clones.  A lengthy chain of copy-on-write snapshots or '
+                    'clones can have a negative impact on performance, but '
+                    'improves space utilization.  0 indicates unlimited '
+                    'clone depth.'),
     cfg.BoolOpt('gpfs_sparse_volumes',
                 default=True,
-                help=('Create volumes as sparse files which take no space. '
-                      'If set to False volume is created as regular file. '
-                      'In this case volume creation may take a significantly '
-                      'longer time.')),
+                help=('Specifies that volumes are created as sparse files '
+                      'which initially consume no space. If set to False, the '
+                      'volume is created as a fully allocated file, in which '
+                      'case, creation may take a significantly longer time.')),
 ]
 CONF = cfg.CONF
 CONF.register_opts(gpfs_opts)

etc/cinder/cinder.conf.sample

@@ -1203,31 +1203,37 @@
 # Options defined in cinder.volume.drivers.gpfs
 #
 
-# Path to the directory on GPFS mount point where volumes are
-# stored (string value)
+# Specifies the path of the GPFS directory where Block Storage
+# volume and snapshot files are stored. (string value)
 #gpfs_mount_point_base=<None>
 
-# Path to GPFS Glance repository as mounted on Nova nodes
-# (string value)
+# Specifies the path of the Image service repository in GPFS.
+# Leave undefined if not storing images in GPFS. (string
+# value)
 #gpfs_images_dir=<None>
 
-# Set this if Glance image repo is on GPFS as well so that the
-# image bits can be transferred efficiently between Glance and
-# Cinder.  Valid values are copy or copy_on_write. copy
-# performs a full copy of the image, copy_on_write efficiently
-# shares unmodified blocks of the image. (string value)
+# Specifies the type of image copy to be used.  Set this when
+# the Image service repository also uses GPFS so that image
+# files can be transferred efficiently from the Image service
+# to the Block Storage service. There are two valid values:
+# "copy" specifies that a full copy of the image is made;
+# "copy_on_write" specifies that copy-on-write optimization
+# strategy is used and unmodified blocks of the image file are
+# shared efficiently. (string value)
 #gpfs_images_share_mode=<None>
 
-# A lengthy chain of copy-on-write snapshots or clones could
-# have impact on performance.  This option limits the number
-# of indirections required to reach a specific block. 0
-# indicates unlimited. (integer value)
+# Specifies an upper limit on the number of indirections
+# required to reach a specific block due to snapshots or
+# clones.  A lengthy chain of copy-on-write snapshots or
+# clones can have a negative impact on performance, but
+# improves space utilization.  0 indicates unlimited clone
+# depth. (integer value)
 #gpfs_max_clone_depth=0
 
-# Create volumes as sparse files which take no space. If set
-# to False volume is created as regular file. In this case
-# volume creation may take a significantly longer time.
-# (boolean value)
+# Specifies that volumes are created as sparse files which
+# initially consume no space. If set to False, the volume is
+# created as a fully allocated file, in which case, creation
+# may take a significantly longer time. (boolean value)
 #gpfs_sparse_volumes=true