Re: Need Warm Fuzzies, ReiserFS (3)

[Tom Vier <tmv@comcast.net>]

On Mon, Dec 20, 2004 at 05:25:03PM +0100, Christian Mayrhuber wrote:
> Disk barriers are only in since 2.6.9, so maybe these get turned on per 
> default after some more testing. That did happen to the data=ordered journal 
> mode.

I was under the impression that they were on by default. I wish this was
documented somewhere; it's very important and i bet a LOT of sysadmins don't
even consider the problems of having write-back caching enabled. At least
most scsi drives come with it disabled by default. There's only wb support
for ata and sata, fwih, too.

A quick grep didn't help me find if there's any other barrier mode other
than flush. It looked like reiserfs had support specifically for flush mode.
I would have thought it'd be done just as a call to something like blkwb().



What about software raid? Are the barriers pushed through the raid layer?



There's been some interesting discussion about this subject on the netbsd
tech-kern list, btw.

-- 
Tom Vier <tmv@comcast.net>
DSA Key ID 0x15741ECE