From owner-freebsd-hackers Fri Mar 3 17:38:19 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from mail4.aracnet.com (mail4.aracnet.com [216.99.193.36]) by hub.freebsd.org (Postfix) with ESMTP id E924637B712 for ; Fri, 3 Mar 2000 17:38:14 -0800 (PST) (envelope-from beattie@aracnet.com) Received: from shell1.aracnet.com (IDENT:root@shell1.aracnet.com [216.99.193.21]) by mail4.aracnet.com (8.9.3/8.9.3) with ESMTP id RAA16182; Fri, 3 Mar 2000 17:38:10 -0800 Received: by shell1.aracnet.com (8.9.3) id RAA12959; Fri, 3 Mar 2000 17:39:55 -0800 Date: Fri, 3 Mar 2000 17:39:55 -0800 (PST) From: Brian Beattie To: Matthew Dillon Cc: Michael Bacarella , Julian Elischer , David Scheidt , freebsd-hackers@FreeBSD.ORG Subject: Re: Copy-on-write filesystem In-Reply-To: <200003040103.RAA12519@apollo.backplane.com> 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 On Fri, 3 Mar 2000, Matthew Dillon wrote: > :> > I think. One problem with "Copy-on-write, when applied to > :> > file copies is that you need to assign the blocks up front, even if you > :> > don't copy the data, as otherwise you could run out of space > :> > when the copy is actually needed. > :> > :> That's the only real drawback I've considered. > :> > :> People accept it (barely) when the OS commits to providing virtual memory > :> it does not have, killing processes when the system falls into debt. > :> > :> No one will appreciate that happening to their "permanent" data, > :> especially if the OS decides that the best way to get out of debt is by > :> deleting a file :) > :> > : > :Actually, since this is copy-on-write, you do not need the block, until > :you write. If you need to make a copy, it will be on a write system call > :(possibly an inode update), just fail the write ENOSPC or whatever. Or am > :I missing something simple here. > > The issue here is to ensure that you have sufficient swap. Swap? I thought we were talking about a copy-on-write filesystem i.e. disk block, not memory, or did I really miss something Brian Beattie | The only problem with beattie@aracnet.com | winning the rat race ... www.aracnet.com/~beattie | in the end you're still a rat To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message