Re: The old raw devices chestnut.

[cutting]
> > >eminently STUPID to claim "file system I/O" is faster: there is
> > >no I/O in that case, just in-memory access!
> >
> > But it will give a faster response therefore "file systems are faster".
>
> Absolutely not. Cache access is faster. And it has nothing to do
> with fs or raw I/O. You get EXACTLY the same speed regardless
> of where you got the data from.

[cutting]

But if the cache is too small or being turned over very quickly the cache will be slower 'cos you to copy from disk to cache and then copy from cache to the app.

Interestingly on the bigger Sun servers the absolute bandwidth to disk is significantly larger than the bandwidth to memory so, in theory, you can the data from disk faster than from memory - I remain unconvinced:-)

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