Re: scsi vs ide performance on fsync's

David Balazic
2001-03-06T19:43:31Z

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