From owner-freebsd-fs@FreeBSD.ORG Tue Aug 28 17:03:07 2007 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 F3C2416A419 for ; Tue, 28 Aug 2007 17:03:06 +0000 (UTC) (envelope-from numisemis@yahoo.com) Received: from web36604.mail.mud.yahoo.com (web36604.mail.mud.yahoo.com [209.191.85.21]) by mx1.freebsd.org (Postfix) with SMTP id B6D6C13C461 for ; Tue, 28 Aug 2007 17:03:06 +0000 (UTC) (envelope-from numisemis@yahoo.com) Received: (qmail 51232 invoked by uid 60001); 28 Aug 2007 17:02:50 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:Date:From:Subject:To:Cc:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding:Message-ID; b=jscHOUf5CKGyC2M8bWVPhov4455Fl8WOVHEcxcuWT2kc8gEvzc2b6VxALOYsQLOFRh129mFcCLmeIkwVzYbgPsWduCwoCBtllBByWa6uMQ5fOPR23Qu5Zxo1Qfzt50VW/vAlee58QbD5sJ9N12mtVNdt3UdfvR5O8j9WsarAIZw=; X-YMail-OSG: _Gv3xSYVM1nzaMF_9StQ_2naZNcHVnZ76LyQOtJoPqqQYy8RtzTL8F8gYfi_jD.dwh_Vkqj3XWiZEFCxb6NQJyrqfbeOcCBaOuxRCEGxaieSRZTp5snGFuYMlMUHNg-- Received: from [85.10.60.49] by web36604.mail.mud.yahoo.com via HTTP; Tue, 28 Aug 2007 10:02:50 PDT Date: Tue, 28 Aug 2007 10:02:50 -0700 (PDT) From: Simun Mikecin To: Pawel Jakub Dawidek In-Reply-To: <20070828105435.GC36596@garage.freebsd.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Message-ID: <397419.50435.qm@web36604.mail.mud.yahoo.com> Cc: freebsd-fs@freebsd.org Subject: Re: zfs and BIO_FLUSH on amr(4) 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: Tue, 28 Aug 2007 17:03:07 -0000 --- Pawel Jakub Dawidek wrote: > On Tue, Aug 28, 2007 at 03:00:44AM -0700, Simun Mikecin wrote: > > amr(4) can have onboard cache memory with or without battery backup. Is BIO_FLUSH call really > > needed when amr(4) is used with onboard cache memory with a battery backup? > I don't think so. The thing is that when ZFS receives information that > write is done, it should be on disk (at some point) and you > battery-backed cache should ensure that. You can turn off sending > BIO_FLUSH by setting vfs.zfs.cache_flush_disable to 1 (in > /boot/loader.conf). > > BTW. How big performance drop do you see with BIO_FLUSH turned on? Not much according to bonnie++: Results from running "bonnie++ -d /var/tmp/test -s 4g -n 100 -u someuser:somegroup" With vfs.zfs.cache_flush_disable=0: Version 1.93c ------Sequential Output------ --Sequential Input- --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP data.home.hr 4G 105 97 57927 15 44814 11 261 97 150219 17 281.0 4 Latency 147ms 1669ms 964ms 83179us 551ms 241ms Version 1.93c ------Sequential Create------ --------Random Create-------- data.home.hr -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 100 19034 92 28638 98 10672 91 13761 98 32042 97 14009 95 Latency 77131us 2460us 3298us 153ms 7728us3796us With vfs.zfs.cache_flush_disable=1: Version 1.93c ------Sequential Output------ --Sequential Input- --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP data.home.hr 4G 118 94 67671 16 41687 10 292 99 154120 20 290.1 4 Latency 764ms 1743ms 1586ms 78276us 342ms 245ms Version 1.93c ------Sequential Create------ --------Random Create-------- data.home.hr -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 100 22064 91 33277 97 13824 93 16720 86 23878 99 10182 95 Latency 68420us 2832us 3789us 727ms 7670us 3838us ____________________________________________________________________________________ Sick sense of humor? Visit Yahoo! TV's Comedy with an Edge to see what's on, when. http://tv.yahoo.com/collections/222