Re: recommendations for stripe/chunk size

[Wolfgang Denk <wd@denx.de>]

In message <47AA08E7.5000801@tmr.com> you wrote:
>
> > I actually  think the kernel should operate with block sizes
> > like this and not wth 4 kiB blocks. It is the readahead and the elevator
> > algorithms that save us from randomly reading 4 kb a time.
> >
> >   
> Exactly, and nothing save a R-A-RW cycle if the write is a partial chunk.

Indeed kernel page size is an important factor in such optimizations.
But you have to keep in mind that this is mostly efficient for (very)
large strictly sequential I/O operations only -  actual  file  system
traffic may be *very* different.

We implemented the option to select kernel page sizes of  4,  16,  64
and  256  kB for some PowerPC systems (440SPe, to be precise). A nice
graphics of the effect can be found here:

https://www.amcc.com/MyAMCC/retrieveDocument/PowerPC/440SPe/RAIDinLinux_PB_0529a.pdf

Best regards,

Wolfgang Denk

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