RepoMirrors
/
mars
mirror of https://github.com/schoebel/mars
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

user-manual: move the state of MARS

This commit is contained in:
Thomas Schoebel-Theuer 2019-09-10 12:55:13 +02:00 committed by Thomas Schoebel-Theuer
parent de9ba2cda3
commit 47544459f0
1 changed files with 100 additions and 100 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

200
docu/mars-user-manual.lyx
View File

@ -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