From owner-freebsd-current Mon Mar 10 7:56:24 2003 Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 3E49837B401 for ; Mon, 10 Mar 2003 07:56:23 -0800 (PST) Received: from stork.mail.pas.earthlink.net (stork.mail.pas.earthlink.net [207.217.120.188]) by mx1.FreeBSD.org (Postfix) with ESMTP id AD6DB43FA3 for ; Mon, 10 Mar 2003 07:56:22 -0800 (PST) (envelope-from tlambert2@mindspring.com) Received: from dialup-209.244.104.52.dial1.sanjose1.level3.net ([209.244.104.52] helo=mindspring.com) by stork.mail.pas.earthlink.net with asmtp (SSLv3:RC4-MD5:128) (Exim 3.33 #1) id 18sPdQ-00000X-00; Mon, 10 Mar 2003 07:56:16 -0800 Message-ID: <3E6CB54D.A8A7F7F0@mindspring.com> Date: Mon, 10 Mar 2003 07:54:53 -0800 From: Terry Lambert X-Mailer: Mozilla 4.79 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: Nuno Teixeira Cc: freebsd-current@freebsd.org Subject: Re: softupdates && write cache && ata tags topic References: <20030308151549.GA622@gw.tex.bogus> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-ELNK-Trace: b1a02af9316fbb217a47c185c03b154d40683398e744b8a468fe5fd3472aef0fcd046b2a633b9fb6350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Nuno Teixeira wrote: > I understand the basic concept of the folowing techs: softupdates, disk > write cache and ata tags. > > My question is: > > It is safe to use softupdates + write cache + ata tags (IBM disk)? > > I read someware that it not safe to use softupdate + write cache > (without ata tags) and if it is not safe why FreeBSD 5.0 ships with them > enabled? See the discussion of 3 weeks ago with one of the engineers from Maxtor, on this list. The short answer is that the drive does not honor tags on a commit to stable storage, before returning the request as satisfied, and that's because on a write, ATA doesn't support disconnect with tagged commands. As to why write caching is on be default, there's a lot of going back and forth on that, and it's flipped state maybe 4-5 times, so far. The short answer is that ATA drives are pig-slow with write caching disabled, and users find that unacceptable. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message