From owner-freebsd-hackers Thu Jun 3 11:42:59 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from uni4nn.gn.iaf.nl (osmium.gn.iaf.nl [193.67.144.12]) by hub.freebsd.org (Postfix) with ESMTP id 81DA515571 for ; Thu, 3 Jun 1999 11:42:56 -0700 (PDT) (envelope-from wilko@yedi.iaf.nl) Received: from yedi.iaf.nl (uucp@localhost) by uni4nn.gn.iaf.nl (8.9.2/8.9.2) with UUCP id TAA20519; Thu, 3 Jun 1999 19:52:13 +0200 (MET DST) Received: (from wilko@localhost) by yedi.iaf.nl (8.9.3/8.9.3) id TAA00693; Thu, 3 Jun 1999 19:34:43 +0200 (CEST) (envelope-from wilko) From: Wilko Bulte Message-Id: <199906031734.TAA00693@yedi.iaf.nl> Subject: Re: The choice of MAXPHYS In-Reply-To: from Zhihui Zhang at "Jun 3, 1999 10:40:10 am" To: zzhang@cs.binghamton.edu Date: Thu, 3 Jun 1999 19:34:43 +0200 (CEST) Cc: freebsd-hackers@FreeBSD.ORG X-Organisation: Private FreeBSD site - Arnhem, The Netherlands X-pgp-info: PGP public key at 'finger wilko@freefall.freebsd.org' X-Mailer: ELM [version 2.4ME+ PL43 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG As Zhihui Zhang wrote ... > > The value of MAXPHYS is chosen to be 64K for the maximum raw I/O transfer > size. I am wondering why it is not set larger. The maxcontig value of FFS > is default to be 16, which means 16*8192 or 128K bytes (twice as big as > 64K) . If we raise the value of MAXPHYS, we can put more data blocks of a > big file contiguously on the disk (perhaps even more than 16 blocks to > achieve better performance). Am I right? Is there any limit of the value > of MAXPHYS? The 64kB limit is a limitation of older SCSI cards. My primary objective to have a > 64kB MAXPHYS is to have larger blocksizes on tape. Especially DLT drives love that ;-) | / o / / _ Arnhem, The Netherlands - Powered by FreeBSD - |/|/ / / /( (_) Bulte WWW : http://www.tcja.nl http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message