Subject: Re: disks write-back cache
To: Manuel Bouyer <>
From: Patrick Welche <>
List: tech-kern
Date: 04/27/2003 15:05:42
On Sat, Apr 26, 2003 at 06:05:27PM +0200, Manuel Bouyer wrote:
> Hi,
> I just discovered that what I though about write-back disk cache on SCSI
> devices was wrong:
> 1) although major unix vendors (tested Sun, DEC/compaq) ships SCSI disks
>    with write-back cache disabled, disks manufacturer don't (I tested
>    various models of SCSI disks coming from a local PC assembler).
> 2) write-back cache affects tagged queuing: with write-back cache enabled,
>    scsi tagged commands can report status completion before the data
>    are written to disk (discovered by experiment).

This is fortuitous! Since the new ahc driver causes rubbish to be written
to my disks, at least this is something to try: tagged queueing is enabled,
and so is write-back cache... Will try switching off write-back cache
on Tuesday...