Re: sync & asyck i/o

[Andre Hedrick]

On Tue, 6 Feb 2001, Stephen C. Tweedie wrote:

> Hi,
> 
> On Tue, Feb 06, 2001 at 05:54:41PM +0000, David Woodhouse wrote:
> > 
> > [e-mail] said:
> > >  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. 
> > 
> > Do we attempt to ask SCSI disks nicely to flush their write caches in this 
> > situation? cf. http://www.danbbs.dk/~dino/SCSI/SCSI2-09.html#9.2.18
> 
> No, we simply omit to instruct them to enable write-back caching.
> Linux assumes that the WCE (write cache enable) bit in a disk's
> caching mode page is zero.

Stephen,

You can not be so blind to omit the command.
You have to issue an active command to disable WCE.
All modern drives come with it defaulted enabled, especially ATA disks.

Andre Hedrick
Linux ATA Development
ASL Kernel Development
-----------------------------------------------------------------------------
ASL, Inc.                                     Toll free: 1-877-ASL-3535
1757 Houret Court                             Fax: [phone]
Milpitas, CA 95035                            Web: www.aslab.com