Re: udma

[Andreas Behnert <abehn@gmx.net>]

Thomas Schönhoff wrote:
> Hallo,
>
> Oliver Beck wrote:
>
> > multcount    = 16 (on)
> Wofür steht dieserWert eigentlich? In der hdparm manpage fand ich den 
> gar nicht erwähnt (oder hab' ihn übersehen!)?
>
> Thomas

Definitiv übersehen :)

man hdparm:

       -m     Get/set sector count for multiple sector I/O on the
              drive.  A setting of 0 disables this feature.  Mul­
              tiple  sector  mode (aka IDE Block Mode), is a fea­
              ture of most modern IDE hard drives, permitting the
              transfer  of  multiple  sectors  per I/O interrupt,
              rather than the usual  one  sector  per  interrupt.
              When  this feature is enabled, it typically reduces
              operating system overhead for disk I/O  by  30-50%.
              On  many  systems,  it also provides increased data
              throughput  of  anywhere  from  5%  to  50%.   Some
              drives,   however   (most  notably  the  WD  Caviar
              series), seem to  run  slower  with  multiple  mode
              enabled.   Your mileage may vary.  Most drives sup­
              port the minimum settings of 2, 4, 8, or  16  (sec­
              tors).   Larger  settings  may  also  be  possible,
              depending on the drive.  A  setting  of  16  or  32
              seems  optimal  on  many  systems.  Western Digital
              recommends lower settings of 4  to  8  on  many  of
              their  drives,  due  tiny  (32kB) drive buffers and
              non-optimized buffering algorithms.   The  -i  flag
              can  be  used to find the maximum setting supported
              by an installed drive (look for MaxMultSect in  the
              output).   Some  drives  claim  to support multiple
              mode, but lose data at some settings.   Under  rare
              circumstances,  such failures can result in massive
              filesystem corruption.


Ich hatte früher mal ein paar Quantum Bigfoot 2,5 GB und diese
unterstützen einen Maximalwert von 64, liefen aber mit -m8 schneller
als mit allen anderen Einstellungen.


Gruß,
ab