From owner-freebsd-fs@freebsd.org Thu Apr 7 01:47:39 2016 Return-Path: Delivered-To: freebsd-fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id B9885B062A2 for ; Thu, 7 Apr 2016 01:47:39 +0000 (UTC) (envelope-from bfriesen@simple.dallas.tx.us) Received: from smtp.simplesystems.org (smtp.simplesystems.org [65.66.246.90]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 8AFBD1A8A for ; Thu, 7 Apr 2016 01:47:39 +0000 (UTC) (envelope-from bfriesen@simple.dallas.tx.us) Received: from freddy.simplesystems.org (freddy.simplesystems.org [65.66.246.65]) by smtp.simplesystems.org (8.14.4+Sun/8.14.4) with ESMTP id u371kSk3005242; Wed, 6 Apr 2016 20:46:28 -0500 (CDT) Date: Wed, 6 Apr 2016 20:46:28 -0500 (CDT) From: Bob Friesenhahn X-X-Sender: bfriesen@freddy.simplesystems.org To: Leo Prasath Arulraj cc: freebsd-fs@freebsd.org Subject: Re: Does ZFS or UFS classify FS Metatada I/O requests with specific BIO_META like flag? In-Reply-To: Message-ID: References: User-Agent: Alpine 2.20 (GSO 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (smtp.simplesystems.org [65.66.246.90]); Wed, 06 Apr 2016 20:46:28 -0500 (CDT) X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Apr 2016 01:47:39 -0000 On Wed, 6 Apr 2016, Leo Prasath Arulraj wrote: > > I want to know if the FreeBSD filesystem UFS and ZFS set any such flag. > From a skim through the source code, it does not seem so because the bio > structure itself does not have any such flag in the first place : > http://fxr.watson.org/fxr/source/sys/bio.h?v=FREEBSD10#L143,144 > > I approciate any help regarding this. Zfs would have no use for any such thing since it does everything in terms of transaction groups (delimited by a disk cache sync of data for involved disks, followed by a TXG write, followed by a disk cache sync). Only synchronous writes get any priority, but they are prioritized by writing to a separate synchronous write log (as well as async/sync data targeted for the current transaction group) so that the request is not lost if the transaction group is otherwise lost. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/