Made spacing after period consistent throughout, removed a couple of spurious commas

doc/source/overview_architecture.rst

@@ -13,9 +13,9 @@ architecture. For each request, it will look up the location of the account,
 container, or object in the ring (see below) and route the request accordingly.
 The public API is also exposed through the Proxy Server.
 
-A large number of failures are also handled in the Proxy Server.  For
+A large number of failures are also handled in the Proxy Server. For
 example, if a server is unavailable for an object PUT, it will ask the
-ring for a handoff server, and route there instead.
+ring for a handoff server and route there instead.
 
 When objects are streamed to or from an object server, they are streamed
 directly through the proxy server to of from the user -- the proxy server
@@ -25,7 +25,7 @@ does not spool them.
 The Ring
 --------
 
-A ring represents a mapping between the names of entities stored on disk, and
+A ring represents a mapping between the names of entities stored on disk and
 their physical location. There are separate rings for accounts, containers, and
 objects. When other components need to perform any operation on an object,
 container, or account, they need to interact with the appropriate ring to
@@ -37,18 +37,18 @@ cluster, and the locations for a partition are stored in the mapping maintained
 by the ring. The ring is also responsible for determining which devices are
 used for handoff in failure scenarios.
 
-Data can be isolated with the concept of zones in the ring.  Each replica
+Data can be isolated with the concept of zones in the ring. Each replica
 of a partition is guaranteed to reside in a different zone. A zone could
 represent a drive, a server, a cabinet, a switch, or even a datacenter.
 
 The partitions of the ring are equally divided among all the devices in the
-Swift installation.  When an event occurs that requires partitions to be
+Swift installation. When partitions need to be moved around (for example if a
-moved around (for example if a device is added to the cluster), the ring
+device is added to the cluster), the ring ensures that a minimum number of
-ensures that a minimum number of partitions are moved at a time, and only
+partitions are moved at a time, and only one replica of a partition is moved at
-one replica of a partition is moved at a time.
+a time.
 
 Weights can be used to balance the distribution of partitions on drives
-across the cluster.  This can be useful, for example, if different sized
+across the cluster. This can be useful, for example, when different sized
 drives are used in a cluster.
 
 The ring is used by the Proxy server and several background processes
@@ -62,24 +62,24 @@ The Object Server is a very simple blob storage server that can store,
 retrieve and delete objects stored on local devices. Objects are stored
 as binary files on the filesystem with metadata stored in the file's
 extended attributes (xattrs). This requires that the underlying filesystem
-choice for object servers must support xattrs on files. Some filesystems,
+choice for object servers support xattrs on files. Some filesystems,
 like ext3, have xattrs turned off by default.
 
 Each object is stored using a path derived from the object name's hash and
-the operation's timestamp.  Last write always wins, and ensures that the
+the operation's timestamp. Last write always wins, and ensures that the
-latest object version will be served.  A deletion is also treated as a
+latest object version will be served. A deletion is also treated as a
 version of the file (a 0 byte file ending with ".ts", which stands for
-tombstone).  This ensures that deleted files are replicated correctly and
+tombstone). This ensures that deleted files are replicated correctly and
 older versions don't magically reappear due to failure scenarios.
 
 ----------------
 Container Server
 ----------------
 
-The Container Server's primary job is to handle listings of objects.  It
+The Container Server's primary job is to handle listings of objects. It
 doesn't know where those object's are, just what objects are in a specific
-container.  The listings are stored as sqlite database files, and replicated
+container. The listings are stored as sqlite database files, and replicated
-across the cluster similar to how objects are.  Statistics are also tracked
+across the cluster similar to how objects are. Statistics are also tracked
 that include the total number of objects, and total storage usage for that
 container.
 
@@ -95,15 +95,15 @@ Replication
 -----------
 
 Replication is designed to keep the system in a consistent state in the face
-of temporary error conditions like network partitions or drive failures.
+of temporary error conditions like network outages or drive failures.
 
 The replication processes compare local data with each remote copy to ensure
 they all contain the latest version. Object replication uses a hash list to
 quickly compare subsections of each partition, and container and account
 replication use a combination of hashes and shared high water marks.
 
-Replication updates are push based.  For object replication, updating is
+Replication updates are push based. For object replication, updating is
-just a matter of rsyncing files to the peer.  Account and container
+just a matter of rsyncing files to the peer. Account and container
 replication push missing records over HTTP or rsync whole database files.
 
 The replicator also ensures that data is removed from the system. When an
@@ -116,9 +116,9 @@ Updaters
 --------
 
 There are times when container or account data can not be immediately
-updated.  This usually occurs during failure scenarios or periods of high
+updated. This usually occurs during failure scenarios or periods of high
-load.  If an update fails, the update is queued locally on the filesystem,
+load. If an update fails, the update is queued locally on the filesystem,
-and the updater will process the failed updates.  This is where an eventual
+and the updater will process the failed updates. This is where an eventual
 consistency window will most likely come in to play. For example, suppose a
 container server is under load and a new object is put in to the system. The
 object will be immediately available for reads as soon as the proxy server
@@ -137,9 +137,9 @@ Auditors
 --------
 
 Auditors crawl the local server checking the integrity of the objects,
-containers, and accounts.  If corruption is found (in the case of bit rot,
+containers, and accounts. If corruption is found (in the case of bit rot,
 for example), the file is quarantined, and replication will replace the bad
-file from another replica.  If other errors are found they are logged (for
+file from another replica. If other errors are found they are logged (for
 example, an object's listing can't be found on any container server it
 should be).