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, 151 insertions, 0 deletions

diff --git a/src/ceph/doc/dev/placement-group.rst b/src/ceph/doc/dev/placement-group.rst
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+============================
+ PG (Placement Group) notes
+============================
+
+Miscellaneous copy-pastes from emails, when this gets cleaned up it
+should move out of /dev.
+
+Overview
+========
+
+PG = "placement group". When placing data in the cluster, objects are
+mapped into PGs, and those PGs are mapped onto OSDs. We use the
+indirection so that we can group objects, which reduces the amount of
+per-object metadata we need to keep track of and processes we need to
+run (it would be prohibitively expensive to track eg the placement
+history on a per-object basis). Increasing the number of PGs can
+reduce the variance in per-OSD load across your cluster, but each PG
+requires a bit more CPU and memory on the OSDs that are storing it. We
+try and ballpark it at 100 PGs/OSD, although it can vary widely
+without ill effects depending on your cluster. You hit a bug in how we
+calculate the initial PG number from a cluster description.
+
+There are a couple of different categories of PGs; the 6 that exist
+(in the original emailer's ``ceph -s`` output) are "local" PGs which
+are tied to a specific OSD. However, those aren't actually used in a
+standard Ceph configuration.
+
+
+Mapping algorithm (simplified)
+==============================
+
+| > How does the Object->PG mapping look like, do you map more than one object on
+| > one PG, or do you sometimes map an object to more than one PG? How about the
+| > mapping of PGs to OSDs, does one PG belong to exactly one OSD?
+| >
+| > Does one PG represent a fixed amount of storage space?
+
+Many objects map to one PG.
+
+Each object maps to exactly one PG.
+
+One PG maps to a single list of OSDs, where the first one in the list
+is the primary and the rest are replicas.
+
+Many PGs can map to one OSD.
+
+A PG represents nothing but a grouping of objects; you configure the
+number of PGs you want, number of OSDs * 100 is a good starting point
+, and all of your stored objects are pseudo-randomly evenly distributed
+to the PGs. So a PG explicitly does NOT represent a fixed amount of
+storage; it represents 1/pg_num'th of the storage you happen to have
+on your OSDs.
+
+Ignoring the finer points of CRUSH and custom placement, it goes
+something like this in pseudocode::
+
+	locator = object_name
+	obj_hash = hash(locator)
+	pg = obj_hash % num_pg
+	OSDs_for_pg = crush(pg)  # returns a list of OSDs
+	primary = osds_for_pg[0]
+	replicas = osds_for_pg[1:]
+
+If you want to understand the crush() part in the above, imagine a
+perfectly spherical datacenter in a vacuum ;) that is, if all OSDs
+have weight 1.0, and there is no topology to the data center (all OSDs
+are on the top level), and you use defaults, etc, it simplifies to
+consistent hashing; you can think of it as::
+
+	def crush(pg):
+	   all_osds = ['osd.0', 'osd.1', 'osd.2', ...]
+	   result = []
+	   # size is the number of copies; primary+replicas
+	   while len(result) < size:
+	       r = hash(pg)
+	       chosen = all_osds[ r % len(all_osds) ]
+	       if chosen in result:
+	           # OSD can be picked only once
+	           continue
+	       result.append(chosen)
+	   return result
+
+User-visible PG States
+======================
+
+.. todo:: diagram of states and how they can overlap
+
+*creating*
+  the PG is still being created
+
+*active*
+  requests to the PG will be processed
+
+*clean*
+  all objects in the PG are replicated the correct number of times
+
+*down*
+  a replica with necessary data is down, so the pg is offline
+
+*replay*
+  the PG is waiting for clients to replay operations after an OSD crashed
+
+*splitting*
+  the PG is being split into multiple PGs (not functional as of 2012-02)
+
+*scrubbing*
+  the PG is being checked for inconsistencies
+
+*degraded*
+  some objects in the PG are not replicated enough times yet
+
+*inconsistent*
+  replicas of the PG are not consistent (e.g. objects are
+  the wrong size, objects are missing from one replica *after* recovery
+  finished, etc.)
+
+*peering*
+  the PG is undergoing the :doc:`/dev/peering` process
+
+*repair*
+  the PG is being checked and any inconsistencies found will be repaired (if possible)
+
+*recovering*
+  objects are being migrated/synchronized with replicas
+
+*recovery_wait*
+  the PG is waiting for the local/remote recovery reservations
+
+*backfilling*
+  a special case of recovery, in which the entire contents of
+  the PG are scanned and synchronized, instead of inferring what
+  needs to be transferred from the PG logs of recent operations
+
+*backfill_wait*
+  the PG is waiting in line to start backfill
+
+*backfill_toofull*
+  backfill reservation rejected, OSD too full
+
+*incomplete*
+  a pg is missing a necessary period of history from its
+  log.  If you see this state, report a bug, and try to start any
+  failed OSDs that may contain the needed information.
+
+*stale*
+  the PG is in an unknown state - the monitors have not received
+  an update for it since the PG mapping changed.
+
+*remapped*
+  the PG is temporarily mapped to a different set of OSDs from what
+  CRUSH specified