From owner-freebsd-hackers Tue Nov 2 15:14: 2 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from bingnet2.cc.binghamton.edu (bingnet2.cc.binghamton.edu [128.226.1.18]) by hub.freebsd.org (Postfix) with ESMTP id 8D9B9154B1 for ; Tue, 2 Nov 1999 15:13:50 -0800 (PST) (envelope-from zzhang@cs.binghamton.edu) Received: from sol.cs.binghamton.edu (cs1-gw.cs.binghamton.edu [128.226.171.72]) by bingnet2.cc.binghamton.edu (8.9.3/8.9.3) with SMTP id SAA16688 for ; Tue, 2 Nov 1999 18:13:49 -0500 (EST) Date: Tue, 2 Nov 1999 17:10:41 -0500 (EST) From: Zhihui Zhang To: freebsd-hackers@freebsd.org Subject: Granularity of disk I/O Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG It is said that the granularity of disk I/O is a sector. I read a little bit of the source code isa/wd.c, which I think is the driver of IDE disks. I find out that the disk can perform multi-block I/O sometimes. Does this mean the granularity of disk I/O can be multi-sector? If the disk can perform DMA, what is the usual DMA size? Is the granularity the DMA size in this case? If a buffer cache is larger than one sector, it should be split into sectors before I/O. If an I/O on a buffer fails, can we tell which sector within that buffer fails? I am confused with these things and it is probably that my questions are confusing too. Any help or hints are appreciated. -Zhihui To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message