From owner-freebsd-hackers@FreeBSD.ORG Wed Jul 10 19:24:40 2013 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id B6BDD948; Wed, 10 Jul 2013 19:24:40 +0000 (UTC) (envelope-from gibbs@FreeBSD.org) Received: from aslan.scsiguy.com (mail.scsiguy.com [70.89.174.89]) by mx1.freebsd.org (Postfix) with ESMTP id 72B8916E5; Wed, 10 Jul 2013 19:24:39 +0000 (UTC) Received: from [192.168.6.139] (207-225-98-3.dia.static.qwest.net [207.225.98.3]) (authenticated bits=0) by aslan.scsiguy.com (8.14.7/8.14.5) with ESMTP id r6AJOWr5098398 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO); Wed, 10 Jul 2013 19:24:32 GMT (envelope-from gibbs@FreeBSD.org) Subject: Re: Make ZFS use the physical sector size when computing initial ashift Mime-Version: 1.0 (Mac OS X Mail 6.5 \(1508\)) Content-Type: text/plain; charset=us-ascii From: "Justin T. Gibbs" X-Priority: 3 In-Reply-To: <97E5A0A8DFBF4F75AAE8EDEFDF849EB0@multiplay.co.uk> Date: Wed, 10 Jul 2013 13:24:26 -0600 Content-Transfer-Encoding: quoted-printable Message-Id: <0A3A05F7-7859-4285-B15A-5E7DDB751062@FreeBSD.org> References: <86zjtupz3r.fsf@nine.des.no> <51DD9801.4090808@delphij.net> <2B9367B6-8759-45C9-B120-9D00A381228F@FreeBSD.org> <97E5A0A8DFBF4F75AAE8EDEFDF849EB0@multiplay.co.uk> To: "Steven Hartland" X-Mailer: Apple Mail (2.1508) X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.4.3 (aslan.scsiguy.com [70.89.174.89]); Wed, 10 Jul 2013 19:24:32 +0000 (UTC) Cc: freebsd-fs@freebsd.org, =?iso-8859-1?Q?Dag-Erling_Sm=F8rgrav?= , d@delphij.net, ivoras@freebsd.org, freebsd-hackers@freebsd.org X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 10 Jul 2013 19:24:40 -0000 On Jul 10, 2013, at 1:06 PM, "Steven Hartland" = wrote: > ----- Original Message ----- From: "Justin T. Gibbs"=20 >> I'm sure lots of folks have "some solution" to this. Here is an >> old version of what we use at Spectra: >> http://people.freebsd.org/~gibbs/zfs_patches/zfs_auto_ashift.diff >> The above patch is missing some cleanup that was motivated by my >> discussions with George Wilson about this change in April. I'll >> dig that up later tonight. Even if you don't read the full diff, >> please read the included checkin comment since it explains the >> motivation behind this particular solution. >>=20 >> This is on my list of things to upstream in the next week or so after >> I add logic to the userspace tools to report whether or not the >> TLVs in a pool are using an optimal allocation size. This is only >> possible if you actually make ZFS fully aware of logical, physical, >> and the configured allocation size. All of the other patches I've = seen >> just treat physical as logical. >=20 > Reading through your patch it seems that your logical_ashift equates = to > the current ashift values which for geom devices is based off = sectorsize > and your physical_ashift is based stripesize. >=20 > This is almost identical to the approach I used adding a "desired = ashift", > which equates to your physical_ashift, along side the standard ashift > i.e. required aka logical_ashift value :) Yes, the approaches are similar. Our current version records the = logical access size in the vdev structure too, which might relate to the issue below. > One issue I did spot in your patch is that you currently expose > zfs_max_auto_ashift as a sysctl but don't clamp its value which would > cause problems should a user configure values > 13. I would expect the zio pipeline to simply insert an ashift aligned = thunking buffer for these operations, but I haven't tried going past an ashift of = 13 in my tests. If it is an issue, it seems the restriction should be based = on logical access size, not optimal access size. -- Justin=