mirror of
https://github.com/ceph/ceph
synced 2024-12-21 10:54:42 +00:00
dc7a2aaf7a
1) ruleset is an obsolete term, and
2) crush-{rule,failure-domain,...} is more descriptive.
Note that we are changing the names of the erasure code profile keys
from ruleset-* to crush-*. We will update this on upgrade when the
luminous flag is set, but that means that during mon upgrade you cannot
create EC pools that use these fields.
When the upgrade completes (users sets require_osd_release = luminous)
existing ec profiles are updated automatically.
Signed-off-by: Sage Weil <sage@redhat.com>
121 lines
3.4 KiB
ReStructuredText
121 lines
3.4 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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<http://jerasure.org>`_ 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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[crush-root={root}] \
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[crush-failure-domain={bucket-type}] \
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[crush-device-class={device-class}] \
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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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``crush-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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``crush-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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``crush-device-class={device-class}``
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:Description: Restrict placement to devices of a specific class (e.g.,
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``ssd`` or ``hdd``), using the crush device class names
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in the CRUSH map.
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:Type: String
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:Required: No.
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:Default:
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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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