From owner-freebsd-fs@FreeBSD.ORG Sun Jun 9 01:04:47 2013 Return-Path: Delivered-To: fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id 2EC1B1C7 for ; Sun, 9 Jun 2013 01:04:47 +0000 (UTC) (envelope-from cross+freebsd@distal.com) Received: from mail.distal.com (mail.distal.com [IPv6:2001:470:e24c:200::ae25]) by mx1.freebsd.org (Postfix) with ESMTP id DB8A41254 for ; Sun, 9 Jun 2013 01:04:46 +0000 (UTC) Received: from magrathea.distal.com (magrathea.distal.com [IPv6:2001:470:e24c:200:ea06:88ff:feca:960e]) (authenticated bits=0) by mail.distal.com (8.14.3/8.14.3) with ESMTP id r5914iip011649 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO); Sat, 8 Jun 2013 21:04:45 -0400 (EDT) Subject: Re: Changing the default for ZFS atime to off? Mime-Version: 1.0 (Mac OS X Mail 6.3 \(1503\)) Content-Type: text/plain; charset=us-ascii From: Chris Ross X-Priority: 3 In-Reply-To: <459E2FCADB4E40079066E4ABDBE47AFE@multiplay.co.uk> Date: Sat, 8 Jun 2013 21:04:44 -0400 Content-Transfer-Encoding: quoted-printable Message-Id: References: <16FEF774EE8E4100AD2CAEC65276A49D@multiplay.co.uk> <20130608213331.GB18201@icarus.home.lan> <01719722FD8A41B4A4366611972A703A@multiplay.co.uk> <20130609001532.GA21540@icarus.home.lan> <459E2FCADB4E40079066E4ABDBE47AFE@multiplay.co.uk> To: "Steven Hartland" X-Mailer: Apple Mail (2.1503) X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.2 (mail.distal.com [IPv6:2001:470:e24c:200::ae25]); Sat, 08 Jun 2013 21:04:45 -0400 (EDT) Cc: fs@freebsd.org X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 09 Jun 2013 01:04:47 -0000 I agree strongly with Jeremy's general opinion. But, am far less = established in the community, so only wanted to make a couple of small points. On Jun 8, 2013, at 20:48 , "Steven Hartland" = wrote: > I guess where I'm coming from is making better for the vast majority. >=20 > I believe there's no point in configuring for a rare case by default > when it will make the much more common case worse. I think the point being made, and certainly in my mind reading this = thread, is that you're considering the "rare" case to be more rare than you = factually know it to be, and more importantly (IMO), you're considering "worse" on something that I consider a very small issue. I understand the reasons = we choose to turn off atime (by adding it to the kernel, at the time, in = 1994) at UUNET for the USENET filesystems. It was just too much activity. But, = for a less than 110% active system, and given the relatively small number of = things that are accessed far more often than they're updated, I just don't = think it's that big of an issue. And, yes, I'm aware of the flash write issue, and I side with turning = off there, though I wouldn't be default. (And, defaulting filesystem parameters = based on some impression of the underlying hardware seems risky at best anyway.) I think there are a small number of cases where it's an issue, and = those people, yourself included, already know how to solve the problem. Myself, = personally, running only small systems, have never turned off atime updates. Don't = feel any need to. For specific heavy-load production systems, _everything_ = is looked at with a fine-toothed-comb. No reason to "default" something = that only those systems need. >> All said and done: I do appreciate having this discussion, = particularly >> publicly on a list. Too many "key changes" in FreeBSD in the past = few >> years have been results of closed-door meetings of sorts (private = mail >> or in-person *con meetings), so the fact this is public is good. >=20 > Everyone has their different uses of any OS, different experience etc, > so things like this need open discussion IMO. I agree very much, and while my opinions may not match many others, = I've been very pleased to read this discussion. Thank you for bringing it = up. - Chris