From owner-freebsd-questions@FreeBSD.ORG Mon May 23 13:17:11 2005 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id E86B316A41C for ; Mon, 23 May 2005 13:17:11 +0000 (GMT) (envelope-from freebsd-questions-local@be-well.ilk.org) Received: from mail27.sea5.speakeasy.net (mail27.sea5.speakeasy.net [69.17.117.29]) by mx1.FreeBSD.org (Postfix) with ESMTP id AF9F443D1D for ; Mon, 23 May 2005 13:17:11 +0000 (GMT) (envelope-from freebsd-questions-local@be-well.ilk.org) Received: (qmail 1040 invoked from network); 23 May 2005 13:17:11 -0000 Received: by simscan 1.1.0 ppid: 1021, pid: 1034, t: 0.1588s scanners: clamav: 0.84/m:31/d:888 Received: from dsl092-078-145.bos1.dsl.speakeasy.net (HELO be-well.ilk.org) ([66.92.78.145]) (envelope-sender ) by mail27.sea5.speakeasy.net (qmail-ldap-1.03) with SMTP for ; 23 May 2005 13:17:11 -0000 Received: by be-well.ilk.org (Postfix, from userid 1147) id 4FEA230; Mon, 23 May 2005 09:17:10 -0400 (EDT) Sender: lowell@be-well.ilk.org To: Rich Winkel References: <200505211757.j4LHvn3M068786@pencil.math.missouri.edu> From: Lowell Gilbert Date: 23 May 2005 09:17:09 -0400 In-Reply-To: <200505211757.j4LHvn3M068786@pencil.math.missouri.edu> Message-ID: <441x7y2iay.fsf@be-well.ilk.org> Lines: 29 User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: freebsd-questions@freebsd.org Subject: Re: 20 snapshot limit per filesystem? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 23 May 2005 13:17:12 -0000 Rich Winkel writes: > Hi, I was just wondering how much overhead would be incurred by increasing > the 20 snapshot limit on mksnap_ffs ? Unfortunately, I don't see a way to give a short answer to that question. On a fairly static filesystem, the answer would be quite small. On a more active filesystem, the number (and size) of different files being modified is more relevant. I tried to do some calculations on my own system, but I kept finding factors that I had overlooked. In practice, it was easier to make my snapshots and see how much disk space and CPU time were used over time. > I use hard links to get snapshot-like functionality under 4.x. I can > recover accidentally deleted files for up to 30 days. I was hoping > I could switch to snapshots without crimping this strategy... You could always try it and see what happens. Or you could change your strategy slightly. I keep weekly snapshots for a few weeks, but daily snapshots only stick around for a week. If you did something like that, you could also keep hourly snapshots for the last few hours. For most users, this kind of approach would be much more likely to have an accidentally deleted file in a snapshot. > By the way, how do snapshots interface with user disk quotas? I assume > files which exist only in a snapshot aren't counted by the quota system. Right.