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authorQiaowei Ren <qiaowei.ren@intel.com>2018-01-04 13:43:33 +0800
committerQiaowei Ren <qiaowei.ren@intel.com>2018-01-05 11:59:39 +0800
commit812ff6ca9fcd3e629e49d4328905f33eee8ca3f5 (patch)
tree04ece7b4da00d9d2f98093774594f4057ae561d4 /src/ceph/doc/rados/operations/erasure-code-jerasure.rst
parent15280273faafb77777eab341909a3f495cf248d9 (diff)
initial code repo
This patch creates initial code repo. For ceph, luminous stable release will be used for base code, and next changes and optimization for ceph will be added to it. For opensds, currently any changes can be upstreamed into original opensds repo (https://github.com/opensds/opensds), and so stor4nfv will directly clone opensds code to deploy stor4nfv environment. And the scripts for deployment based on ceph and opensds will be put into 'ci' directory. Change-Id: I46a32218884c75dda2936337604ff03c554648e4 Signed-off-by: Qiaowei Ren <qiaowei.ren@intel.com>
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+============================
+Jerasure erasure code plugin
+============================
+
+The *jerasure* plugin is the most generic and flexible plugin, it is
+also the default for Ceph erasure coded pools.
+
+The *jerasure* plugin encapsulates the `Jerasure
+<http://jerasure.org>`_ library. It is
+recommended to read the *jerasure* documentation to get a better
+understanding of the parameters.
+
+Create a jerasure profile
+=========================
+
+To create a new *jerasure* erasure code profile::
+
+ ceph osd erasure-code-profile set {name} \
+ plugin=jerasure \
+ k={data-chunks} \
+ m={coding-chunks} \
+ technique={reed_sol_van|reed_sol_r6_op|cauchy_orig|cauchy_good|liberation|blaum_roth|liber8tion} \
+ [crush-root={root}] \
+ [crush-failure-domain={bucket-type}] \
+ [crush-device-class={device-class}] \
+ [directory={directory}] \
+ [--force]
+
+Where:
+
+``k={data chunks}``
+
+:Description: Each object is split in **data-chunks** parts,
+ each stored on a different OSD.
+
+:Type: Integer
+:Required: Yes.
+:Example: 4
+
+``m={coding-chunks}``
+
+:Description: Compute **coding chunks** for each object and store them
+ on different OSDs. The number of coding chunks is also
+ the number of OSDs that can be down without losing data.
+
+:Type: Integer
+:Required: Yes.
+:Example: 2
+
+``technique={reed_sol_van|reed_sol_r6_op|cauchy_orig|cauchy_good|liberation|blaum_roth|liber8tion}``
+
+:Description: The more flexible technique is *reed_sol_van* : it is
+ enough to set *k* and *m*. The *cauchy_good* technique
+ can be faster but you need to chose the *packetsize*
+ carefully. All of *reed_sol_r6_op*, *liberation*,
+ *blaum_roth*, *liber8tion* are *RAID6* equivalents in
+ the sense that they can only be configured with *m=2*.
+
+:Type: String
+:Required: No.
+:Default: reed_sol_van
+
+``packetsize={bytes}``
+
+:Description: The encoding will be done on packets of *bytes* size at
+ a time. Chosing the right packet size is difficult. The
+ *jerasure* documentation contains extensive information
+ on this topic.
+
+:Type: Integer
+:Required: No.
+:Default: 2048
+
+``crush-root={root}``
+
+:Description: The name of the crush bucket used for the first step of
+ the ruleset. For intance **step take default**.
+
+:Type: String
+:Required: No.
+:Default: default
+
+``crush-failure-domain={bucket-type}``
+
+:Description: Ensure that no two chunks are in a bucket with the same
+ failure domain. For instance, if the failure domain is
+ **host** no two chunks will be stored on the same
+ host. It is used to create a ruleset step such as **step
+ chooseleaf host**.
+
+:Type: String
+:Required: No.
+:Default: host
+
+``crush-device-class={device-class}``
+
+:Description: Restrict placement to devices of a specific class (e.g.,
+ ``ssd`` or ``hdd``), using the crush device class names
+ in the CRUSH map.
+
+:Type: String
+:Required: No.
+:Default:
+
+ ``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
+
+``--force``
+
+:Description: Override an existing profile by the same name.
+
+:Type: String
+:Required: No.
+