From owner-freebsd-scsi@FreeBSD.ORG Tue Jun 14 11:22:12 2005 Return-Path: X-Original-To: freebsd-scsi@freebsd.org Delivered-To: freebsd-scsi@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 6F6CD16A41F for ; Tue, 14 Jun 2005 11:22:12 +0000 (GMT) (envelope-from bde@zeta.org.au) Received: from mailout1.pacific.net.au (mailout1.pacific.net.au [61.8.0.84]) by mx1.FreeBSD.org (Postfix) with ESMTP id E155243D53 for ; Tue, 14 Jun 2005 11:22:11 +0000 (GMT) (envelope-from bde@zeta.org.au) Received: from mailproxy1.pacific.net.au (mailproxy1.pacific.net.au [61.8.0.86]) by mailout1.pacific.net.au (8.13.4/8.13.4/Debian-1) with ESMTP id j5EBM2iB024372; Tue, 14 Jun 2005 21:22:02 +1000 Received: from katana.zip.com.au (katana.zip.com.au [61.8.7.246]) by mailproxy1.pacific.net.au (8.13.4/8.13.4/Debian-1) with ESMTP id j5EBLxOg027395; Tue, 14 Jun 2005 21:22:00 +1000 Date: Tue, 14 Jun 2005 21:22:01 +1000 (EST) From: Bruce Evans X-X-Sender: bde@delplex.bde.org To: Glenn Dawson In-Reply-To: <6.1.0.6.2.20050613235825.09e52810@cobalt.antimatter.net> Message-ID: <20050614211046.G38218@delplex.bde.org> References: <20050608171130.GA64736@over-yonder.net> <1118252322.7479.28.camel@zappa.Chelsea-Ct.Org> <20050609113616.I41471@p-i-n.com> <20050609130511.GA732@uk.tiscali.com> <20050610162814.A25098@p-i-n.com> <20050610150718.GA7005@nargothrond.kdm.org> <20050612002508.B25098@p-i-n.com> <20050612035440.GA21262@nargothrond.kdm.org> <20050613121915.C25098@p-i-n.com> <20050614015958.GA33865@nargothrond.kdm.org> <42AE5ED7.8070309@samsco.org> <6.1.0.6.2.20050613235825.09e52810@cobalt.antimatter.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-scsi@freebsd.org Subject: Re: Accessing SCSI-Devices >2TB X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 14 Jun 2005 11:22:12 -0000 On Tue, 14 Jun 2005, Glenn Dawson wrote: > This is a little OT for this thread, but I'm currently trying to solve a > problem which might be related to the aac driver, so I'll toss this out there > and see if anyone has any ideas for me. It seems to be very OT :-). > It trying to make the transition from 4.x to 5.x I've noticed that > performance of the md(4) (in 5.x) driver seems to be much worse than the > vn(4) driver under 4.x. > > Here's the scenario: > > A pair of mirrored disks on an adaptec 2120S using the aac(4) driver is being > used to house files that are the backing store for a number of virtual disks. > Each file is typically about 4GB. > > Under 4.11 using the vn(4) driver I see throughput of about 17MB/sec when > writing to one of the virtual disks (using dd). > > Under 5.4 using the md(4) driver I only see throughput of about 7MB/sec when > writing to the virtual disk. This seems to be from sync writes now being the default for md. Try using "mdconfig -o async ...". I will reply with more details to your message in freebsd-performnance. Bruce