diff --git a/docu/mars-architecture-guide.lyx b/docu/mars-architecture-guide.lyx index 9773b6fd..34d470ce 100644 --- a/docu/mars-architecture-guide.lyx +++ b/docu/mars-architecture-guide.lyx @@ -7141,7 +7141,7 @@ yes \begin_inset Text \begin_layout Plain Layout -Replication parallelism (per gran.) +Replication parallelism (per gran.) \end_layout \end_inset @@ -7503,6 +7503,62 @@ The last item means that ZFS by itself does not protect against amok-running enterprise-critical applications. \end_layout +\begin_layout Standard +\noindent +\begin_inset Graphics + filename images/MatieresCorrosives.png + lyxscale 50 + scale 17 + +\end_inset + + In simple words: the +\series bold +ability for butterfly +\series default + is non-trivial to achieve. + It can easily turn into a nightmare, if you would try to establish it on + top of larger +\family typewriter +zfs +\family default + installations. + Although termed +\begin_inset Quotes eld +\end_inset + +replication +\begin_inset Quotes erd +\end_inset + +, it is more similar to +\begin_inset Quotes eld +\end_inset + +backup +\begin_inset Quotes erd +\end_inset + +. +\end_layout + +\begin_layout Standard +\noindent +\begin_inset Graphics + filename images/MatieresCorrosives.png + lyxscale 50 + scale 17 + +\end_inset + + Known +\family typewriter +zfs +\family default + replication setups at sisters of 1&1 are lacking the butterfly ability, + likely due to these difficulties. +\end_layout + \begin_layout Standard \noindent \begin_inset Graphics @@ -7512,12 +7568,39 @@ The last item means that ZFS by itself does not protect against amok-running \end_inset -Notice that zfs snapshots can be combined with DRBD or MARS, because zfs + +\begin_inset Graphics + filename images/lightbulb_brightlit_benj_.png + lyxscale 12 + scale 7 + +\end_inset + + +\begin_inset Graphics + filename images/lightbulb_brightlit_benj_.png + lyxscale 12 + scale 7 + +\end_inset + + Notice that +\family typewriter +zfs +\family default + snapshots can be +\series bold +easily combined +\series default + with DRBD or MARS, because +\family typewriter +zfs +\family default snapshots are residing at \emph on filesystem \emph default - layer, while DRBD / MARS replicas are located at + layer, while DRBD / MARS replicas are located at the lower \emph on block \emph default @@ -7526,11 +7609,43 @@ block \emph on top \emph default - of DRBD or MARS virtual devices, and import / export them + of DRBD or MARS virtual devices, and use +\family typewriter +zpool import +\family default + / +\family typewriter +export +\family default + \emph on individually \emph default - upon handover / failover of each LV. + at handover / failover of each LV. + A relatively easy way for implemention is the +\family typewriter +systemd +\family default + interface of MARS (see the according section in +\family typewriter +mars-user-manual.pdf +\family default +). + You just need to write +\emph on +once +\emph default + a small unit template file, containing a few +\family typewriter +zpool +\family default + commands. + This small template will then be automatically instantiated for each resource + by the +\family typewriter +marsadm +\family default + macro processor, as often as needed. \end_layout \begin_layout Standard @@ -7546,17 +7661,15 @@ individually \series bold \emph on fundamental -\series default \emph default - difference between zpools and classical RAID / LVM stacked architectures. + difference +\series default + between zpools and classical RAID / LVM stacked architectures. Some zfs advocates are propagating zpools as a replacement for both RAID and LVM. - However, there is a -\series bold -massive difference -\series default - in architecture, as explained in the following example (10 logical resources - over 48 physical spindles), achieving practically the + However, there is a massive difference in architecture, as illustrated + in the following example (10 logical resources over 48 physical spindles), + achieving practically the \series bold \emph on same @@ -7643,8 +7756,12 @@ monolithic status open \begin_layout Plain Layout -Some sysadmins acting as zfs advocates are reclaiming this as an advantage, - because they need to understand only a single tool for managing +Some sysadmins acting as +\family typewriter +zfs +\family default + advocates are reclaiming this as an advantage, because they need to understand + only a single tool for managing \begin_inset Quotes eld \end_inset @@ -7667,18 +7784,53 @@ true architecture \series default as seen from outside. +\end_layout + +\begin_layout Standard +\noindent +\begin_inset Graphics + filename images/MatieresCorrosives.png + lyxscale 50 + scale 17 + +\end_inset + This violates the classical \emph on layering rules \emph default - from Dijkstra. - In contrast, classical LVM-based configurations are + from Dijkstra (see section +\begin_inset CommandInset ref +LatexCommand nameref +reference "subsec:Layering-Rules" +plural "false" +caps "false" +noprefix "false" + +\end_inset + +). + In contrast, classical LVM-based configurations (see section +\begin_inset CommandInset ref +LatexCommand nameref +reference "par:Positive-Example:-ShaHoLin" +plural "false" +caps "false" +noprefix "false" + +\end_inset + + or the example setup in +\family typewriter +mars-user-manual.pdf +\family default +) are \series bold component oriented \series default , according to the \series bold -Unix philosophy +Unix Philosophy \series default . \end_layout