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https://github.com/ceph/ceph
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99 lines
2.4 KiB
ReStructuredText
99 lines
2.4 KiB
ReStructuredText
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============================================
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cephfs -- ceph file system options utility
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============================================
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.. program:: cephfs
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Synopsis
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========
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| **cephfs** [ *path* *command* *options* ]
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Description
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===========
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**cephfs** is a control utility for accessing and manipulating file
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layout and location data in the Ceph distributed file system.
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.. TODO format this like a proper man page
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Choose one of the following three commands:
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- ``show_layout`` View the layout information on a file or directory
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- ``set_layout`` Set the layout information on a file or directory
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- ``show_location`` View the location information on a file
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Options
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=======
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Your applicable options differ depending on whether you are setting or viewing layout/location.
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Viewing options:
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----------------
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.. option:: -l --offset
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Specify an offset for which to retrieve location data
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Setting options:
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----------------
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.. option:: -u --stripe_unit
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Set the size of each stripe
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.. option:: -c --stripe_count
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Set the number of stripes per object
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.. option:: -s --object_size
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Set the size of the objects to stripe across
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.. option:: -p --pool
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Set the pool (by numeric value, not name!) to use
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.. option:: -o --osd
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Set the preferred OSD to use as the primary
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Limitations
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===========
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When setting layout data, the specified stripe unit and stripe count
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must multiply to the size of an object. Any parameters you don't set
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explicitly are left at the system defaults.
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Obviously setting the layout of a file and a directory means different
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things. Setting the layout of a file specifies exactly how to place
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the individual file. This must be done before writing *any* data to
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it. Truncating a file does not allow you to change the layout either.
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Setting the layout of a directory sets the "default layout", which is
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used to set the file layouts on any files subsequently created in the
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directory (or any subdirectory). Pre-existing files do not have their
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layouts changed.
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You'll notice that the layout information allows you to specify a
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preferred OSD for placement. This is allowed but is not recommended
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since it can dramatically unbalance your storage cluster's space
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utilization.
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Availability
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============
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**cephfs** is part of the Ceph distributed file system. Please refer
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to the Ceph wiki at http://ceph.newdream.net/wiki for more
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information.
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See also
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========
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:doc:`ceph <ceph>`\(8)
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