diff --git a/docu/mars-user-manual.lyx b/docu/mars-user-manual.lyx index ace3234d..8c0628fc 100644 --- a/docu/mars-user-manual.lyx +++ b/docu/mars-user-manual.lyx @@ -853,6 +853,106 @@ fast-backward rewinding, of course at some cost. \end_layout +\begin_layout Section +The State of MARS +\begin_inset CommandInset label +LatexCommand label +name "sec:The-State-of" + +\end_inset + + +\end_layout + +\begin_layout Standard +In general, MARS tries to +\emph on +hide +\emph default + any network failures from you as best as it can. + After a network problem, any internal low-level socket connections are + +\emph on +transparently +\emph default + tried to re-open ASAP, without need for sysadmin intervention. + In difference to DRBD, network failures will +\emph on +not +\emph default + automatically alter the state of MARS, such as switching to +\family typewriter +disconnected +\family default + after a +\family typewriter +ko_timeout +\family default + or similar. + From a high-level sysadmin viewpoint, communication may just take a very + long time to succeed. +\end_layout + +\begin_layout Standard +When the behaviour of MARS is different from DRBD, it is usually intended + as a feature. +\end_layout + +\begin_layout Standard +MARS is not only an +\series bold +asynchronous +\series default + system at block IO level, but also +\series bold +at control level +\series default +. +\end_layout + +\begin_layout Standard +This is +\emph on +necessary +\emph default + because in a widely distributed long-distance system running on slow or + even temporarily failing networks, actions may take a long time, and there + may be many actions +\series bold +started in parallel +\series default +. +\end_layout + +\begin_layout Standard +\begin_inset Graphics + filename images/lightbulb_brightlit_benj_.png + lyxscale 12 + scale 7 + +\end_inset + +Synchronous concepts are generally not sufficient for expressing that. + Because of inherent asynchronicity and of dynamic creation / joining of + resources, it is neither possible to comprehensively depict a complex distribut +ed MARS system, nor a comprehensive standalone snippet of MARS, as a finite + state transition diagram +\begin_inset Foot +status open + +\begin_layout Plain Layout +Probably it could be possible to formally model MARS as a Petri net. + However, complete Petri nets are tending to become very conplex, and to + describe lots of low-level details. + Expressing hierarchy, in a top-down fashion, is cumbersome. + We find no clue in trying to do so. +\end_layout + +\end_inset + +. +\end_layout + \begin_layout Chapter HOWTO setup MARS \begin_inset CommandInset label @@ -31921,106 +32021,6 @@ Old Structure (TO DISAPPEAR) Quick Start Guide \end_layout -\begin_layout Section -The State of MARS -\begin_inset CommandInset label -LatexCommand label -name "sec:The-State-of" - -\end_inset - - -\end_layout - -\begin_layout Standard -In general, MARS tries to -\emph on -hide -\emph default - any network failures from you as best as it can. - After a network problem, any internal low-level socket connections are - -\emph on -transparently -\emph default - tried to re-open ASAP, without need for sysadmin intervention. - In difference to DRBD, network failures will -\emph on -not -\emph default - automatically alter the state of MARS, such as switching to -\family typewriter -disconnected -\family default - after a -\family typewriter -ko_timeout -\family default - or similar. - From a high-level sysadmin viewpoint, communication may just take a very - long time to succeed. -\end_layout - -\begin_layout Standard -When the behaviour of MARS is different from DRBD, it is usually intended - as a feature. -\end_layout - -\begin_layout Standard -MARS is not only an -\series bold -asynchronous -\series default - system at block IO level, but also -\series bold -at control level -\series default -. -\end_layout - -\begin_layout Standard -This is -\emph on -necessary -\emph default - because in a widely distributed long-distance system running on slow or - even temporarily failing networks, actions may take a long time, and there - may be many actions -\series bold -started in parallel -\series default -. -\end_layout - -\begin_layout Standard -\begin_inset Graphics - filename images/lightbulb_brightlit_benj_.png - lyxscale 12 - scale 7 - -\end_inset - -Synchronous concepts are generally not sufficient for expressing that. - Because of inherent asynchronicity and of dynamic creation / joining of - resources, it is neither possible to comprehensively depict a complex distribut -ed MARS system, nor a comprehensive standalone snippet of MARS, as a finite - state transition diagram -\begin_inset Foot -status open - -\begin_layout Plain Layout -Probably it could be possible to formally model MARS as a Petri net. - However, complete Petri nets are tending to become very conplex, and to - describe lots of low-level details. - Expressing hierarchy, in a top-down fashion, is cumbersome. - We find no clue in trying to do so. -\end_layout - -\end_inset - -. -\end_layout - \begin_layout Standard Although MARS tries to \emph on