Re: sync & asyck i/o

From: Stephen C. Tweedie (
Date: Tue Feb 06 2001 - 12:34:37 EST


On Tue, Feb 06, 2001 at 02:52:40PM +0000, Alan Cox wrote:
> > According to the man page for fsync it copies in-core data to disk
> > prior to its return. Does that take async i/o to the media in account?
> > I.e. does it wait for completion of the async i/o to the disk?
> Undefined.

> In practice some IDE disks do write merging and small amounts of write
> caching in the drive firmware so you cannot trust it 100%.

It's worth noting that it *is* defined unambiguously in the standards:
fsync waits until all the data is hard on disk. Linux will obey that
if it possibly can: only in cases where the hardware is actively lying
about when the data has hit disk will the guarantee break down.

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This archive was generated by hypermail 2b29 : Wed Feb 07 2001 - 21:00:24 EST