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author | Qiaowei Ren <qiaowei.ren@intel.com> | 2018-01-04 13:43:33 +0800 |
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committer | Qiaowei Ren <qiaowei.ren@intel.com> | 2018-01-05 11:59:39 +0800 |
commit | 812ff6ca9fcd3e629e49d4328905f33eee8ca3f5 (patch) | |
tree | 04ece7b4da00d9d2f98093774594f4057ae561d4 /src/ceph/doc/rados/operations/erasure-code-jerasure.rst | |
parent | 15280273faafb77777eab341909a3f495cf248d9 (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>
Diffstat (limited to 'src/ceph/doc/rados/operations/erasure-code-jerasure.rst')
-rw-r--r-- | src/ceph/doc/rados/operations/erasure-code-jerasure.rst | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/src/ceph/doc/rados/operations/erasure-code-jerasure.rst b/src/ceph/doc/rados/operations/erasure-code-jerasure.rst new file mode 100644 index 0000000..e8da097 --- /dev/null +++ b/src/ceph/doc/rados/operations/erasure-code-jerasure.rst @@ -0,0 +1,120 @@ +============================ +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. + |