devel: Fix a few reST issues in object-storage.rst

docs/devel/architecture/object-storage.rst

@@ -6,55 +6,56 @@ Object Storage Overview
 The Object Storage: Contents
 ----------------------------
 
-All the history and context of the archive is represented by 
+All the history and context of the archive is represented by
 a graph (Merkle DAG) with the following nodes types:
-  - releases, 
-  - revisions (commits)
-  - directories
-  - directory entries (file names) 
 
-This graph is stored in a database, commonly called "Graph" or 
-"Storage". 
+- releases,
+- revisions (commits)
+- directories
+- directory entries (file names)
 
-This database is currently based on PostgreSQL, and is going 
-to be migrated to Cassandra, which is more efficient in terms of 
+This graph is stored in a database, commonly called "Graph" or
+"Storage".
+
+This database is currently based on PostgreSQL, and is going
+to be migrated to Cassandra, which is more efficient in terms of
 concurrent writing.
 
-The source code itself (the content of the files) represents a huge 
-volume of data, and one can find exactly the same content in different 
-files. In order to avoid storing several times the same content, 
-contents are deduplicated: a single content is stored only once, 
-and all the files entries having this exact content will refer to the 
+The source code itself (the content of the files) represents a huge
+volume of data, and one can find exactly the same content in different
+files. In order to avoid storing several times the same content,
+contents are deduplicated: a single content is stored only once,
+and all the files entries having this exact content will refer to the
 same content.
 
 Ceph
 ----
 
-These contents are stored in a customized file system, called 
-"Object Storage", each content being considered as an object. 
-Until now, the actual object storage is based on an open source 
-File System technology called ZFS. 
+These contents are stored in a customized file system, called
+"Object Storage", each content being considered as an object.
+Until now, the actual object storage is based on an open source
+File System technology called ZFS.
 
-The growth of the archive requires a more adapted technology, 
-and an few years ago, we chose Ceph, a distributed Storage 
+The growth of the archive requires a more adapted technology,
+and an few years ago, we chose Ceph, a distributed Storage
 technology created by RedHat.
 
-A specificity of Software Heritage is that each content has a 
-small size (half of our contents are less than 3KB), which is 
-much smaller than the minimum space used by Ceph to store a 
-single file (16KB). 
+A specificity of Software Heritage is that each content has a
+small size (half of our contents are less than 3KB), which is
+much smaller than the minimum space used by Ceph to store a
+single file (16KB).
 Using Ceph directly would hence result in a massive waste of space.
 
 Winery
 ------
 
-So we needed to create a custom layer on top of Ceph to group 
-the data we store, using sharding techniques: a shard is a Ceph 
-object that contains many contents. In order to be able to retrieve 
-the single contents, we need to handle a mechanism that enables to 
+So we needed to create a custom layer on top of Ceph to group
+the data we store, using sharding techniques: a shard is a Ceph
+object that contains many contents. In order to be able to retrieve
+the single contents, we need to handle a mechanism that enables to
 know where the content is located in the shard.
 
-This layer is called Winery, and was developed especially for 
+This layer is called Winery, and was developed especially for
 Software Heritage by Easter Eggs.
 
-.. thumbnail:: ../images/object-storage.svg
\ No newline at end of file
+.. thumbnail:: ../images/object-storage.svg