Remove N chains stuff from section 13 for clarity

doc/src.high-level/high-level-chain-mgr.tex

@@ -23,8 +23,8 @@
 \copyrightdata{978-1-nnnn-nnnn-n/yy/mm} 
 \doi{nnnnnnn.nnnnnnn}
 
-\titlebanner{Draft \#0.9, May 2014}
+\titlebanner{Draft \#0.91, June 2014}
-\preprintfooter{Draft \#0.9, May 2014}
+\preprintfooter{Draft \#0.91, June 2014}
 
 \title{Chain Replication metadata management in Machi, an immutable
   file store}
@@ -1453,22 +1453,19 @@ $
       \underbrace{T_1}_\textbf{Tail \#1}}^\textbf{Chain \#1 (U.P.~Invariant preserving)}
 \mid
 \overbrace{H_2, M_{21},\ldots,
-      \underbrace{T_2}_\textbf{Tail \#2}}^\textbf{Chain \#2 (repairing)}
+      \underbrace{T_2}_\textbf{Tail \#2 \& Tail of Tails ($T_{tails}$)}}^\textbf{Chain \#2 (repairing)}
-\mid \ldots \mid
-\overbrace{H_n, M_{n1},\ldots,
-      \underbrace{T_n}_\textbf{Tail \#n \& Tail of Tails ($T_{tails}$)}}^\textbf{Chain \#n (repairing)}
 ]
 $
 \caption{A general representation of a ``chain of chains'': a chain prefix of
   Update Propagation Invariant preserving FLUs (``Chain \#1'')
-  with FLUs from an arbitrary $n-1$ other chains under repair.}
+  with FLUs under repair (``Chain \#2'').}
 \label{fig:repair-chain-of-chains}
 \end{figure*}
 
 Both situations can cause data loss if handled incorrectly.
 If a violation of the Update Propagation Invariant (see end of
 Section~\ref{sec:cr-proof}) is permitted, then the strong consistency
-guarantee of Chain Replication is violated.  Machi uses
+guarantee of Chain Replication can be violated.  Machi uses
 write-once registers, so the number of possible strong consistency
 violations is smaller than Chain Replication of mutable registers.
 However, even when using write-once registers,
@@ -1509,10 +1506,9 @@ as the foundation for Machi's data loss prevention techniques.
 \centering
 $
 [\overbrace{\underbrace{H_1}_\textbf{Head}, M_{11}, T_1,
-                        H_2, M_{21}, T_2,
+                        H_2, M_{21},
                         \ldots
-                        H_n, M_{n1},
+                        \underbrace{T_2}_\textbf{Tail}}^\textbf{Chain (U.P.~Invariant preserving)}
-                        \underbrace{T_n}_\textbf{Tail}}^\textbf{Chain (U.P.~Invariant preserving)}
 ]
 $
 \caption{Representation of Figure~\ref{fig:repair-chain-of-chains}
@@ -1523,7 +1519,7 @@ $
 
 Machi's repair process must preserve the Update Propagation
 Invariant.  To avoid data races with data copying from
-``U.P.~Invariant preserving'' servers (i.e. fully repaired with
+``U.P.~Invariant-preserving'' servers (i.e. fully repaired with
 respect to the Update Propagation Invariant)
 to servers of unreliable/unknown state, a
 projection like the one shown in
@@ -1533,7 +1529,7 @@ projection of this type.
 
 \begin{itemize}
 
-\item The system maintains the distinction between ``U.P.~preserving''
+\item The system maintains the distinction between ``U.P.~Invariant-preserving''
   and ``repairing'' FLUs at all times.  This allows the system to
   track exactly which servers are known to preserve the Update
   Propagation Invariant and which servers do not.
@@ -1546,6 +1542,9 @@ projection of this type.
   to the ``tail of tails''.  This rule also includes any
   repair operations.
 
+\item All read operations that require strong consistency are directed
+  to Tail \#1, as usual.
+
 \end{itemize}
 
 While normal operations are performed by the cluster, a file
@@ -1558,7 +1557,7 @@ mode of the system.
 In cases where the cluster is operating in CP Mode,
 CORFU's repair method of ``just copy it all'' (from source FLU to repairing
 FLU) is correct, {\em except} for the small problem pointed out in
-Section~\ref{sub:repair-divergence}.  The problem for Machi is one of
+Appendix~\ref{sub:repair-divergence}.  The problem for Machi is one of
 time \& space.  Machi wishes to avoid transferring data that is
 already correct on the repairing nodes.  If a Machi node is storing
 170~TBytes of data, we really do not wish to use 170~TBytes of bandwidth
@@ -1588,10 +1587,9 @@ algorithm proposed is:
 
 \item For chain \#1 members, i.e., the
   leftmost chain relative to Figure~\ref{fig:repair-chain-of-chains},
-  repair files byte ranges for any chain \#1 members that are not members
+  repair all file byte ranges for any chain \#1 members that are not members
   of the {\tt FLU\_List} set.  This will repair any partial
-  writes to chain \#1 that were unsuccessful (e.g., client crashed).
+  writes to chain \#1 that were interrupted, e.g., by a client crash.
-  (Note however that this step only repairs FLUs in chain \#1.)
 
 \item For all file byte ranges $B$ in all files on all FLUs in all repairing
   chains where Tail \#1's value is written, send repair data $B$
@@ -1689,10 +1687,19 @@ paper.
 \section{Acknowledgements}
 
 We wish to thank everyone who has read and/or reviewed this document
-in its really-terrible early drafts and have helped improve it
+in its really terrible early drafts and have helped improve it
-immensely: Justin Sheehy, Kota Uenishi, Shunichi Shinohara, Andrew
+immensely:
-Stone, Jon Meredith, Chris Meiklejohn, John Daily, Mark Allen, and Zeeshan
+Mark Allen,
-Lakhani.
+John Daily,
+Zeeshan Lakhani,
+Chris Meiklejohn,
+Jon Meredith,
+Mark Raugas,
+Justin Sheehy,
+Shunichi Shinohara,
+Andrew Stone,
+and
+Kota Uenishi.
 
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