From owner-freebsd-hackers Sun Mar 5 0:49:14 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from verdi.nethelp.no (verdi.nethelp.no [158.36.41.162]) by hub.freebsd.org (Postfix) with SMTP id 146EA37B99E for ; Sun, 5 Mar 2000 00:49:07 -0800 (PST) (envelope-from sthaug@nethelp.no) Received: (qmail 57771 invoked by uid 1001); 5 Mar 2000 08:49:01 +0000 (GMT) To: kc5vdj@swbell.net, jbryant@ppp-207-193-2-159.kscymo.swbell.net Cc: mbac@nyct.net, freebsd-hackers@FreeBSD.ORG Subject: Re: Copy-on-write filesystem From: sthaug@nethelp.no In-Reply-To: Your message of "Fri, 03 Mar 2000 20:45:18 -0600 (CST)" References: <200003040245.UAA10031@ppp-207-193-2-159.kscymo.swbell.net> X-Mailer: Mew version 1.05+ on Emacs 19.34.2 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Date: Sun, 05 Mar 2000 09:49:01 +0100 Message-ID: <57769.952246141@verdi.nethelp.no> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > > Imagine: cp file file2, file and file2 reference the same exact blocks, > > but modified chunks of file2 would be given their own private blocks. > > This is not a microsoft innovation, actually, I believe it was a VMS > innovation. It's called a generational filesystem. the original is > stored, and later generations of the file are stored as diffs. As far as I know, VMS simply stores whole files - no diffs involved. Now if you go back to for instance Univac 1100 and the Exec-8 OS (I suppose it is OS-1100 now), you'll find a system that *did* store the diffs. In the form of punched card images! :-) Steinar Haug, Nethelp consulting, sthaug@nethelp.no To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message