From owner-freebsd-fs@FreeBSD.ORG Fri Nov 25 12:27:45 2011 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id DD68F106566B; Fri, 25 Nov 2011 12:27:45 +0000 (UTC) (envelope-from lev@freebsd.org) Received: from onlyone.friendlyhosting.spb.ru (onlyone.friendlyhosting.spb.ru [IPv6:2a01:4f8:131:60a2::2]) by mx1.freebsd.org (Postfix) with ESMTP id 7D4308FC08; Fri, 25 Nov 2011 12:27:45 +0000 (UTC) Received: from lion.home.serebryakov.spb.ru (unknown [IPv6:2001:470:923f:1:5974:a369:b987:bc4d]) (Authenticated sender: lev@serebryakov.spb.ru) by onlyone.friendlyhosting.spb.ru (Postfix) with ESMTPA id 43E6B4AC1C; Fri, 25 Nov 2011 16:27:44 +0400 (MSK) Date: Fri, 25 Nov 2011 16:27:38 +0400 From: Lev Serebryakov X-Priority: 3 (Normal) Message-ID: <1798256069.20111125162738@serebryakov.spb.ru> To: Kostik Belousov In-Reply-To: <20111125113756.GZ50300@deviant.kiev.zoral.com.ua> References: <1957615267.20111123230026@serebryakov.spb.ru> <20111123194444.GE50300@deviant.kiev.zoral.com.ua> <20111125110235.GB1642@garage.freebsd.pl> <20111125113756.GZ50300@deviant.kiev.zoral.com.ua> MIME-Version: 1.0 Content-Type: text/plain; charset=windows-1251 Content-Transfer-Encoding: quoted-printable Cc: freebsd-fs@freebsd.org, Pawel Jakub Dawidek Subject: Re: Does UFS2 send BIO_FLUSH to GEOM when update metadata (with softupdates)? X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 Nov 2011 12:27:45 -0000 Hello, Kostik. You wrote 25 =ED=EE=FF=E1=F0=FF 2011 =E3., 15:37:56: > Harware that reports finished write and not making the data to stable > storage, or software driver that does such thing itself are just > utterly broken. Ok, than any modern hardware, especially high-performance one, is "utterly broken". We need to live with this. Almost all this hardware provide some knobs to fix situation in critical cases -- flags for synchronious write, etc. FFS/SU/SU_J doesn't use these knobs. All such flags are lost on "struct buf" <-> "str= uct bio" boundary. I like patch from ivoars@, and even more like approach with new flag for BIO and changes in ATA and SCSI drivers to support this. And my geom_raid5, which NEEDS write cache, too. Alexander Motin (mav@), AHCI driver author and person, who do a lot of work in GEOM now, agree with me (I could provide you with quotes from off-list message exchange in Russian). He agrees to add support for this flag to AHCI/ATA layer, if it will be introduced. IMHO, something should be done here. And this ``should be done'' is not ``somebody should done this.'' I could do coding, testing (but not excessive performance one 00 I don't have enough spare hardware), mav@ seems to be ready to make performance tests. But here is one trick: FFS2/SU code is very fragile, and I will need supervision from FFS guru. And if FFS guru thinks, that all storage hardware in world should be fixed (in pricv of huge perofrmance degradation), and FFS/SU is Ok as-is, it will be impossible. --=20 // Black Lion AKA Lev Serebryakov