Re: scsi vs ide performance on fsync's

[David Balazic <david.balazic@uni-mb.si>]

Linus Torvalds himself wrote :

> On Tue, 6 Mar 2001, Alan Cox wrote: 
> > 
> > > > I don't know if there is any way to turn of a write buffer on an IDE disk. 
> > > You want a forced set of commands to kill caching at init? 
> > 
> > Wrong model 
> > 
> > You want a write barrier. Write buffering (at least for short intervals) in 
> > the drive is very sensible. The kernel needs to able to send drivers a write 
> > barrier which will not be completed with outstanding commands before the 
> > barrier. 
> 
> Agreed. 
> 
> Write buffering is incredibly useful on a disk - for all the same reasons 
> that an OS wants to do it. The disk can use write buffering to speed up 
> writes a lot - not just lower the _perceived_ latency by the OS, but to 
> actually improve performance too. 
> 
> But Alan is right - we needs a "sync" command or something. I don't know 
> if IDE has one (it already might, for all I know). 

ATA , SCSI and ATAPI all have a FLUSH_CACHE command. (*)
Whether the drives implement it is another question ...

(*) references : 
  ATA-6 draft standard from www.t13.org
  MtFuji document from ????????


-- 
David Balazic
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"Be excellent to each other." - Bill & Ted
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