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user-manual: rework IO performance tuning

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Thomas Schoebel-Theuer 2019-09-10 10:01:51 +02:00 committed by Thomas Schoebel-Theuer
parent c14b288a4a
commit b88f787c24
1 changed files with 28 additions and 2 deletions
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docu/mars-user-manual.lyx
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@ -25070,6 +25070,12 @@ re-ordering of writeback
transaction logfile, and even when both are residing at the same RAID set. transaction logfile, and even when both are residing at the same RAID set.
\end_layout \end_layout
\begin_layout Standard
Since RAID-6 is has more expensive write operations due to its CRC computations
and updates, RAID-6 will much more profit from this effect.
Other RAID modes like RAID-10 may show a lower throughput improvement.
\end_layout
\begin_layout Standard \begin_layout Standard
Notice: this effect is not only dependent from total RAM size and from the Notice: this effect is not only dependent from total RAM size and from the
maximum size of the MARS temporary memory buffer (tuning parameter maximum size of the MARS temporary memory buffer (tuning parameter
@ -25098,6 +25104,17 @@ dd
is no appropriate benchmarking tool, and has almost nothing to do with is no appropriate benchmarking tool, and has almost nothing to do with
real workloads occuring in datacenters, which typically are neither sequential, real workloads occuring in datacenters, which typically are neither sequential,
nor do they have a parallelism degree of only 1. nor do they have a parallelism degree of only 1.
\end_layout
\begin_layout Standard
\noindent
\begin_inset Graphics
filename images/MatieresCorrosives.png
lyxscale 50
scale 17
\end_inset
Please don't try to lead any discussions about this: simply use Please don't try to lead any discussions about this: simply use
\family typewriter \family typewriter
blktrace blktrace
@ -25123,11 +25140,20 @@ dd
\end_inset \end_inset
Any assumptions about workloads are very dangerous: they can deviate from Any
practice not only by factors, but sometimes even by \series bold
assumptions about workloads
\series default
are very dangerous: they can deviate from practice not only by factors,
but sometimes even by
\emph on \emph on
orders of magnitude orders of magnitude
\emph default \emph default
.
There no substitute for real measuments of
\series bold
actual workload behaviour
\series default
. .
\end_layout \end_layout