From owner-freebsd-current Sat Feb 20 13:17:40 1999 Delivered-To: freebsd-current@freebsd.org Received: from feral.com (feral.com [192.67.166.1]) by hub.freebsd.org (Postfix) with ESMTP id D6BE211830 for ; Sat, 20 Feb 1999 13:16:30 -0800 (PST) (envelope-from mjacob@feral.com) Received: from localhost (mjacob@localhost) by feral.com (8.8.7/8.8.7) with ESMTP id NAA32079; Sat, 20 Feb 1999 13:15:49 -0800 Date: Sat, 20 Feb 1999 13:15:48 -0800 (PST) From: Matthew Jacob X-Sender: mjacob@feral-gw Reply-To: mjacob@feral.com To: Matthew Dillon Cc: Paul van der Zwan , "Kenneth D. Merry" , freebsd-current@FreeBSD.ORG Subject: Re: Slow seq. write on Seagate ST36530N In-Reply-To: <199902202058.MAA11080@apollo.backplane.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Well, yes, it can if the number of tagged commands you throw at a device overloads the sequencer so it can never really get started on the first command. If you don't disconnect, you don't throw multiple commands at the disk. I don't remember from the original mail whether or not this was a raw device or not. On Sat, 20 Feb 1999, Matthew Dillon wrote: > :This did not improve anything , but I think I have found the couse. > :In that modepage there is a DISC value which was 0 on the IBM and 1 on the > :Seagate. I remembered a ' Enable disconnect' option in the Adaptec 2940 bios, > :setting this to 'off' for both harddisks led to a huge performance increase on > :the Seagate. If I also enable Ultra mode iozone write goes from 1.5 MB/s > :to 12 MB/s ( a factor of 8 !!!). > : > : Paul > : > :-- > :Paul van der Zwan paulz @ trantor.xs4all.nl > > There's something wrong. Disconnection should not cause that sort > of performance decrease. Disconnection is necessary if you want to > maintain preformance with more then one scsi device on the scsi bus. > > -Matt > Matthew Dillon > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-current" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message