Date: Wed, 28 Aug 2002 22:04:52 +1000 From: Antony Mawer <ajmawer@optusnet.com.au> To: freebsd-stable@FreeBSD.ORG Subject: write cache not actually disabled by sysctl? Message-ID: <3D6CBC64.7050205@optusnet.com.au>
next in thread | raw e-mail | index | archive | help
After reading about the potential dangers assocaited with enabling the
write cache on ATA drives in combination with softupdates, I've recently
added the following to /boot/loader.conf:
hw.ata.wc="0"
Once booted, running sysctl confirms that this is set:
[root@gibson] ~# sysctl hw.ata.wc
hw.ata.wc: 0
However, looking at the atacontrol cap output, it appears that write
caching is still enabled on both ATA drives (see below). Can I trust the
information from atacontrol cap to be accurate? And if so, why is write
caching enabled when the sysctl is explicitly set to off? The system was
rebooted after adding the change to loader.conf to allow it to take
effect...
I'm not overly worried by sacrificing some performance for potentially
increased safety gains as disabling write caching involves...
Any thoughts?
-Antony
[atacontrol output below]
[root@gibson] ~# atacontrol cap 2 0
ATA channel 2, Master, device ad4:
ATA/ATAPI revision 5
device model ExcelStor Technology CT210
firmware revision ES4CA53D
cylinders 16383
heads 16
sectors/track 63
lba supported 20040450 sectors
lba48 not supported
dma supported
overlap not supported
Feature Support Enable Value Vendor
write cache yes yes
read ahead yes yes
dma queued no no 0/00
SMART yes no
microcode download yes yes
security yes no
power management yes yes
advanced power management no no 0/00
automatic acoustic management no no 0/00 0/00
[root@gibson] ~# atacontrol cap 3 0
ATA channel 3, Master, device ad6:
ATA/ATAPI revision 5
device model QUANTUM FIREBALLlct20 10
firmware revision APL.0900
cylinders 16383
heads 16
sectors/track 63
lba supported 20044080 sectors
lba48 not supported
dma supported
overlap not supported
Feature Support Enable Value Vendor
write cache yes yes
read ahead yes yes
dma queued no no 0/00
SMART yes no
microcode download yes yes
security yes no
power management yes yes
advanced power management no no 0/00
automatic acoustic management yes no 0/00 0/00
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-stable" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?3D6CBC64.7050205>