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110 lines
3.1 KiB
ReStructuredText
110 lines
3.1 KiB
ReStructuredText
============================
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Jerasure erasure code plugin
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============================
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The *jerasure* plugin is the most generic and flexible plugin, it is
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also the default for Ceph erasure coded pools.
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The *jerasure* plugin encapsulates the `Jerasure
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<https://bitbucket.org/jimplank/jerasure/>`_ library. It is
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recommended to read the *jerasure* documentation to get a better
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understanding of the parameters.
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Create a jerasure profile
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=========================
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To create a new *jerasure* erasure code profile::
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ceph osd erasure-code-profile set {name} \
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plugin=jerasure \
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k={data-chunks} \
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m={coding-chunks} \
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technique={reed_sol_van|reed_sol_r6_op|cauchy_orig|cauchy_good|liberation|blaum_roth|liber8tion} \
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[ruleset-root={root}] \
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[ruleset-failure-domain={bucket-type}] \
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[directory={directory}] \
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[--force]
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Where:
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``k={data chunks}``
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:Description: Each object is split in **data-chunks** parts,
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each stored on a different OSD.
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:Type: Integer
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:Required: Yes.
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:Example: 4
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``m={coding-chunks}``
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:Description: Compute **coding chunks** for each object and store them
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on different OSDs. The number of coding chunks is also
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the number of OSDs that can be down without losing data.
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:Type: Integer
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:Required: Yes.
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:Example: 2
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``technique={reed_sol_van|reed_sol_r6_op|cauchy_orig|cauchy_good|liberation|blaum_roth|liber8tion}``
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:Description: The more flexible technique is *reed_sol_van* : it is
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enough to set *k* and *m*. The *cauchy_good* technique
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can be faster but you need to chose the *packetsize*
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carefully. All of *reed_sol_r6_op*, *liberation*,
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*blaum_roth*, *liber8tion* are *RAID6* equivalents in
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the sense that they can only be configured with *m=2*.
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:Type: String
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:Required: No.
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:Default: reed_sol_van
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``packetsize={bytes}``
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:Description: The encoding will be done on packets of *bytes* size at
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a time. Chosing the right packet size is difficult. The
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*jerasure* documentation contains extensive information
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on this topic.
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:Type: Integer
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:Required: No.
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:Default: 2048
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``ruleset-root={root}``
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:Description: The name of the crush bucket used for the first step of
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the ruleset. For intance **step take default**.
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:Type: String
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:Required: No.
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:Default: default
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``ruleset-failure-domain={bucket-type}``
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:Description: Ensure that no two chunks are in a bucket with the same
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failure domain. For instance, if the failure domain is
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**host** no two chunks will be stored on the same
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host. It is used to create a ruleset step such as **step
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chooseleaf host**.
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:Type: String
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:Required: No.
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:Default: host
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``directory={directory}``
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:Description: Set the **directory** name from which the erasure code
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plugin is loaded.
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:Type: String
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:Required: No.
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:Default: /usr/lib/ceph/erasure-code
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``--force``
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:Description: Override an existing profile by the same name.
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:Type: String
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:Required: No.
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