From owner-freebsd-fs@FreeBSD.ORG Mon Dec 28 01:24:05 2009 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 41B2D1065672 for ; Mon, 28 Dec 2009 01:24:05 +0000 (UTC) (envelope-from jroberson@jroberson.net) Received: from mail-yw0-f197.google.com (mail-yw0-f197.google.com [209.85.211.197]) by mx1.freebsd.org (Postfix) with ESMTP id 058048FC1B for ; Mon, 28 Dec 2009 01:24:04 +0000 (UTC) Received: by ywh35 with SMTP id 35so1734836ywh.7 for ; Sun, 27 Dec 2009 17:23:57 -0800 (PST) Received: by 10.91.50.3 with SMTP id c3mr2873881agk.71.1261963437775; Sun, 27 Dec 2009 17:23:57 -0800 (PST) Received: from ?10.0.1.198? (udp022762uds.hawaiiantel.net [72.234.79.107]) by mx.google.com with ESMTPS id 15sm5066227gxk.8.2009.12.27.17.23.55 (version=SSLv3 cipher=RC4-MD5); Sun, 27 Dec 2009 17:23:56 -0800 (PST) Date: Sun, 27 Dec 2009 15:25:35 -1000 (HST) From: Jeff Roberson X-X-Sender: jroberson@desktop To: patpro In-Reply-To: <3ea87f5f62bb8ba30d798d4605a64c83@localhost> Message-ID: References: <32CA2B73-3412-49DD-9401-4773CC73BED0@patpro.net> <4B3283F2.7060804@barryp.org> <3ea87f5f62bb8ba30d798d4605a64c83@localhost> User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-fs@freebsd.org Subject: Re: snapshot implementation X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 28 Dec 2009 01:24:05 -0000 On Fri, 25 Dec 2009, patpro wrote: > > On Wed, 23 Dec 2009 14:56:18 -0600, Barry Pederson wrote: >> "...there's virtually no overhead at all due to the copy-on-write >> architecture. In fact, sometimes it is faster to take a snapshot rather >> than free the blocks containing the old data!" >> >> That's certainly not the case with UFS snapshots, which can take a long >> time to complete (we're talking freezing your machine's disk activity >> for many minutes), and are limited to 20 total. > > > UFS uses copy on write. But you say many minutes to complete? Don't you > speak about dump(1), that uses snapshot as a basis to dump a live file > system? > I agree, UFS snapshot creation is not lightning-fast, but many minutes > seems a lot to me, and I never experienced such a long creation time. It can take some time depending on fs activity on the machine. There are ways to continue to optimize it within the existing infrastructure. It only requires someone willing to expend the time. Jeff > > patpro > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" >