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>

1 files changed, 82 insertions, 0 deletions

diff --git a/src/ceph/doc/dev/osd_internals/erasure_coding.rst b/src/ceph/doc/dev/osd_internals/erasure_coding.rst
new file mode 100644
index 0000000..7263cc3
--- /dev/null
+++ b/src/ceph/doc/dev/osd_internals/erasure_coding.rst
@@ -0,0 +1,82 @@
+==============================
+Erasure Coded Placement Groups
+==============================
+
+Glossary
+--------
+
+*chunk* 
+   when the encoding function is called, it returns chunks of the same
+   size. Data chunks which can be concatenated to reconstruct the original
+   object and coding chunks which can be used to rebuild a lost chunk.
+
+*chunk rank*
+   the index of a chunk when returned by the encoding function. The
+   rank of the first chunk is 0, the rank of the second chunk is 1
+   etc.
+
+*stripe* 
+   when an object is too large to be encoded with a single call,
+   each set of chunks created by a call to the encoding function is
+   called a stripe.
+
+*shard|strip*
+   an ordered sequence of chunks of the same rank from the same
+   object.  For a given placement group, each OSD contains shards of
+   the same rank. When dealing with objects that are encoded with a
+   single operation, *chunk* is sometime used instead of *shard*
+   because the shard is made of a single chunk. The *chunks* in a
+   *shard* are ordered according to the rank of the stripe they belong
+   to.
+
+*K*
+   the number of data *chunks*, i.e. the number of *chunks* in which the
+   original object is divided. For instance if *K* = 2 a 10KB object
+   will be divided into *K* objects of 5KB each.
+
+*M* 
+   the number of coding *chunks*, i.e. the number of additional *chunks*
+   computed by the encoding functions. If there are 2 coding *chunks*, 
+   it means 2 OSDs can be out without losing data.
+
+*N*
+   the number of data *chunks* plus the number of coding *chunks*, 
+   i.e. *K+M*.
+
+*rate*
+   the proportion of the *chunks* that contains useful information, i.e. *K/N*.
+   For instance, for *K* = 9 and *M* = 3 (i.e. *K+M* = *N* = 12) the rate is 
+   *K* = 9 / *N* = 12 = 0.75, i.e. 75% of the chunks contain useful information.
+
+The definitions are illustrated as follows (PG stands for placement group):
+::
+ 
+                 OSD 40                       OSD 33
+       +-------------------------+ +-------------------------+
+       |      shard 0 - PG 10    | |      shard 1 - PG 10    |
+       |+------ object O -------+| |+------ object O -------+|
+       ||+---------------------+|| ||+---------------------+||
+ stripe|||    chunk  0         ||| |||    chunk  1         ||| ...
+   0   |||    stripe 0         ||| |||    stripe 0         ||| 
+       ||+---------------------+|| ||+---------------------+||
+       ||+---------------------+|| ||+---------------------+||
+ stripe|||    chunk  0         ||| |||    chunk  1         ||| ...
+   1   |||    stripe 1         ||| |||    stripe 1         |||
+       ||+---------------------+|| ||+---------------------+||
+       ||+---------------------+|| ||+---------------------+||
+ stripe|||    chunk  0         ||| |||    chunk  1         ||| ...
+   2   |||    stripe 2         ||| |||    stripe 2         |||
+       ||+---------------------+|| ||+---------------------+||
+       |+-----------------------+| |+-----------------------+|
+       |         ...             | |         ...             |
+       +-------------------------+ +-------------------------+
+
+Table of content
+----------------
+
+.. toctree::
+   :maxdepth: 1
+
+   Developer notes <erasure_coding/developer_notes>
+   Jerasure plugin <erasure_coding/jerasure>
+   High level design document <erasure_coding/ecbackend>