Date: Thu, 18 Nov 2004 14:05:51 GMT From: Arne Wörner <arne_woerner@yahoo.com> To: freebsd-gnats-submit@FreeBSD.org Subject: i386/74074: hw.ata.wc=0 / but write cache still enabled Message-ID: <200411181405.iAIE5pqa053338@www.freebsd.org> Resent-Message-ID: <200411181410.iAIEARVE028663@freefall.freebsd.org>
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>Number: 74074
>Category: i386
>Synopsis: hw.ata.wc=0 / but write cache still enabled
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-i386
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Thu Nov 18 14:10:27 GMT 2004
>Closed-Date:
>Last-Modified:
>Originator: Arne Wörner
>Release: R5.3
>Organization:
>Environment:
FreeBSD neo.riddick.homeunix.org. 5.3-RELEASE FreeBSD 5.3-RELEASE #0: Thu Nov 11 17:27:53 UTC 2004 aw@neo.riddick.homeunix.org.:/usr/obj/usr/src/sys/RIDDICK i386
>Description:
I wanted to turn of ATA disc write caching (by setting hw.ata.wc to zero):
but after a boot after power on atacontrol cap 0 0 still says, that the write cache feature is enabled:
write cache yes yes
while sysctl says, that hw.ata.wc is 0:
# sysctl hw.ata.wc
hw.ata.wc: 0
I think this is a bug, that can be security relevant in the case of a power failure or system crash (at least if one is using a filesystem with soft updates enabled).
After a reboot (warm) the write cache is sometimes disabled but sometimes enabled... :-(
>How-To-Repeat:
1. shutdown the box
2. turn off power
3. turn on power
4. look at hw.ata.wc
5. look ata atacontrol's output
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
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