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Remove N chains stuff from section 13 for clarity

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Scott Lystig Fritchie 2015-06-17 09:28:07 +09:00
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doc/src.high-level/high-level-chain-mgr.tex
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@ -23,8 +23,8 @@
\copyrightdata{978-1-nnnn-nnnn-n/yy/mm}
\doi{nnnnnnn.nnnnnnn}
\titlebanner{Draft \#0.9, May 2014}
\preprintfooter{Draft \#0.9, May 2014}
\titlebanner{Draft \#0.91, June 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)}
\mid \ldots \mid
\overbrace{H_n, M_{n1},\ldots,
\underbrace{T_n}_\textbf{Tail \#n \& Tail of Tails ($T_{tails}$)}}^\textbf{Chain \#n (repairing)}
\underbrace{T_2}_\textbf{Tail \#2 \& Tail of Tails ($T_{tails}$)}}^\textbf{Chain \#2 (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_n}_\textbf{Tail}}^\textbf{Chain (U.P.~Invariant preserving)}
\underbrace{T_2}_\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).
(Note however that this step only repairs FLUs in chain \#1.)
writes to chain \#1 that were interrupted, e.g., by a client crash.
\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
immensely: Justin Sheehy, Kota Uenishi, Shunichi Shinohara, Andrew
Stone, Jon Meredith, Chris Meiklejohn, John Daily, Mark Allen, and Zeeshan
Lakhani.
in its really terrible early drafts and have helped improve it
immensely:
Mark Allen,
John Daily,
Zeeshan Lakhani,
Chris Meiklejohn,
Jon Meredith,
Mark Raugas,
Justin Sheehy,
Shunichi Shinohara,
Andrew Stone,
and
Kota Uenishi.
\bibliographystyle{abbrvnat}
\begin{thebibliography}{}