From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Vier Subject: Re: Need Warm Fuzzies, ReiserFS (3) Date: Mon, 20 Dec 2004 14:23:25 -0500 Message-ID: <20041220192325.GB12169@zero> References: <41C66615.5010206@simutronics.com> <200412201331.25180.christian.mayrhuber@gmx.net> <20041220153840.GA11409@zero> <200412201725.03216.christian.mayrhuber@gmx.net> Reply-To: Tom Vier Mime-Version: 1.0 Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com Content-Disposition: inline In-Reply-To: <200412201725.03216.christian.mayrhuber@gmx.net> List-Id: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Christian Mayrhuber Cc: reiserfs-list@namesys.com 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 DSA Key ID 0x15741ECE