+++ /dev/null
-=====================
-Erasure code profiles
-=====================
-
-Erasure code is defined by a **profile** and is used when creating an
-erasure coded pool and the associated crush ruleset.
-
-The **default** erasure code profile (which is created when the Ceph
-cluster is initialized) provides the same level of redundancy as two
-copies but requires 25% less disk space. It is described as a profile
-with **k=2** and **m=1**, meaning the information is spread over three
-OSD (k+m == 3) and one of them can be lost.
-
-To improve redundancy without increasing raw storage requirements, a
-new profile can be created. For instance, a profile with **k=10** and
-**m=4** can sustain the loss of four (**m=4**) OSDs by distributing an
-object on fourteen (k+m=14) OSDs. The object is first divided in
-**10** chunks (if the object is 10MB, each chunk is 1MB) and **4**
-coding chunks are computed, for recovery (each coding chunk has the
-same size as the data chunk, i.e. 1MB). The raw space overhead is only
-40% and the object will not be lost even if four OSDs break at the
-same time.
-
-.. _list of available plugins:
-
-.. toctree::
- :maxdepth: 1
-
- erasure-code-jerasure
- erasure-code-isa
- erasure-code-lrc
- erasure-code-shec
-
-osd erasure-code-profile set
-============================
-
-To create a new erasure code profile::
-
- ceph osd erasure-code-profile set {name} \
- [{directory=directory}] \
- [{plugin=plugin}] \
- [{stripe_unit=stripe_unit}] \
- [{key=value} ...] \
- [--force]
-
-Where:
-
-``{directory=directory}``
-
-:Description: Set the **directory** name from which the erasure code
- plugin is loaded.
-
-:Type: String
-:Required: No.
-:Default: /usr/lib/ceph/erasure-code
-
-``{plugin=plugin}``
-
-:Description: Use the erasure code **plugin** to compute coding chunks
- and recover missing chunks. See the `list of available
- plugins`_ for more information.
-
-:Type: String
-:Required: No.
-:Default: jerasure
-
-``{stripe_unit=stripe_unit}``
-
-:Description: The amount of data in a data chunk, per stripe. For
- example, a profile with 2 data chunks and stripe_unit=4K
- would put the range 0-4K in chunk 0, 4K-8K in chunk 1,
- then 8K-12K in chunk 0 again. This should be a multiple
- of 4K for best performance. The default value is taken
- from the monitor config option
- ``osd_pool_erasure_code_stripe_unit`` when a pool is
- created. The stripe_width of a pool using this profile
- will be the number of data chunks multiplied by this
- stripe_unit.
-
-:Type: String
-:Required: No.
-
-``{key=value}``
-
-:Description: The semantic of the remaining key/value pairs is defined
- by the erasure code plugin.
-
-:Type: String
-:Required: No.
-
-``--force``
-
-:Description: Override an existing profile by the same name, and allow
- setting a non-4K-aligned stripe_unit.
-
-:Type: String
-:Required: No.
-
-osd erasure-code-profile rm
-============================
-
-To remove an erasure code profile::
-
- ceph osd erasure-code-profile rm {name}
-
-If the profile is referenced by a pool, the deletion will fail.
-
-osd erasure-code-profile get
-============================
-
-To display an erasure code profile::
-
- ceph osd erasure-code-profile get {name}
-
-osd erasure-code-profile ls
-===========================
-
-To list the names of all erasure code profiles::
-
- ceph osd erasure-code-profile ls
-
Code Review / stor4nfv.git / blobdiff