From owner-freebsd-fs Tue Feb 27 21:39:08 1996 Return-Path: owner-fs Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id VAA12929 for fs-outgoing; Tue, 27 Feb 1996 21:39:08 -0800 (PST) Received: from who.cdrom.com (who.cdrom.com [192.216.222.3]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id VAA12924 for ; Tue, 27 Feb 1996 21:39:06 -0800 (PST) Received: from rocky.sri.MT.net ([204.182.243.10]) by who.cdrom.com (8.6.12/8.6.11) with ESMTP id VAA22237 for ; Tue, 27 Feb 1996 21:39:04 -0800 Received: (from nate@localhost) by rocky.sri.MT.net (8.6.12/8.6.12) id WAA06665; Tue, 27 Feb 1996 22:40:23 -0700 Date: Tue, 27 Feb 1996 22:40:23 -0700 From: Nate Williams Message-Id: <199602280540.WAA06665@rocky.sri.MT.net> To: adrian@virginia.edu Cc: Peter Stubbs , Peter van Heusden , freebsd-fs@freebsd.org Subject: Re: Compressing filesystem for FreeBSD In-Reply-To: References: <6BD18783D77@aidan.staidan.qld.edu.au> Sender: owner-fs@freebsd.org Precedence: bulk > > The real problem with compressing a file system that is often > forgotten is that you are increasing the cost in CPU cycles for a disk > I/O. I don't think it's at all forgotten. I think that folks are willing to take the performance hit for the decrease in disk space for files that are rarely accessed. > While I have had dos/linux enthusiasts go on about how compressing > your filesystem can both improve I/O bandwidth and increase available disk > space, the cost is often fogotten. While I do know that compressed FS often do increase I/O under DOS due to stupid disk layouts, I haven't heard many 'compression' proponents claim that it increases I/O on real FS. > On a multi-user system, the CPU is not idle during disk I/O. Depends. On my SCSI system it might be, depending on the load. > I think there would also be problems with paging and reads in general. > Which block of the disk contains the nth byte? In short, I don't see > it being worth the effort. On my laptop it would *certainly* be worth the effort. I've got cycles to burn since I'm the only user, and I'm more than willing to get free disk space for my cycles. On my multi-user system, I'm more than willing to take the performance hit for our local archives which are rarely accessed by take up a huge amount of space. I think most folks who are serious about this understand the costs, and are willing to pay them for certain applications. Nate