From owner-freebsd-hackers Sun Jun 6 15:25:31 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from gizmo.internode.com.au (gizmo.internode.com.au [192.83.231.115]) by hub.freebsd.org (Postfix) with ESMTP id D214D150BA for ; Sun, 6 Jun 1999 15:25:22 -0700 (PDT) (envelope-from newton@gizmo.internode.com.au) Received: (from newton@localhost) by gizmo.internode.com.au (8.9.3/8.9.3) id HAA36050; Mon, 7 Jun 1999 07:54:16 +0930 (CST) (envelope-from newton) From: Mark Newton Message-Id: <199906062224.HAA36050@gizmo.internode.com.au> Subject: Re: allocate file blocks contiguously To: zzhang@cs.binghamton.edu (Zhihui Zhang) Date: Mon, 7 Jun 1999 07:54:16 +0930 (CST) Cc: farshid@bol.sharif.ac.ir, freebsd-hackers@FreeBSD.ORG In-Reply-To: from "Zhihui Zhang" at Jun 6, 99 10:40:01 am X-Mailer: ELM [version 2.4 PL25] 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 Zhihui Zhang wrote: > My feeling is that if we allocate ALL the data blocks of a big file > contiguously, this will lead to "too much localization" as described in > the paper (or the book). However, this may be good for this big file if > the system buffering capability and hardware allow it (at the cost of > other files?) Maybe this is something we could get if XFS is ported: XFS's guaranteed rate I/O (partly) works by putting guaranteed-rate files on distinct positions on the disk, or different "subvolumes" in the case of GRIO on XLV logical volumes. So when preparing a filesystem you could build a logical volume out of twenty 9 Gbyte disks plus another five 9 Gbyte disks for guaranteed-rate files. [ in practice you'd probably be building such a filesystem for a specific application, though, so you'd probably really use 25 9 Gbyte disks for GRIO :-) ] You decide which subvolume a file is allocated to immediately after file creation: There's an ioctl() which can be used before the first write to a new file which sets the "please make me fast" flag. One thing that helps to make this possible is an I/O scheduler which supports prioritization. Hmm... - mark ---- Mark Newton Email: newton@internode.com.au (W) Network Engineer Email: newton@atdot.dotat.org (H) Internode Systems Pty Ltd Desk: +61-8-82232999 "Network Man" - Anagram of "Mark Newton" Mobile: +61-416-202-223 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message