From owner-freebsd-questions@FreeBSD.ORG Wed Mar 30 15:59:29 2005 Return-Path: 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 0086C16A4CE for ; Wed, 30 Mar 2005 15:59:29 +0000 (GMT) Received: from parrot.aev.net (host29-15.pool8174.interbusiness.it [81.74.15.29]) by mx1.FreeBSD.org (Postfix) with ESMTP id 9FDCD43D53 for ; Wed, 30 Mar 2005 15:59:27 +0000 (GMT) (envelope-from ml.diespammer@netfence.it) Received: from soth.ventu (adsl-223-56.38-151.net24.it [151.38.56.223]) (authenticated bits=128) by parrot.aev.net (8.13.1/8.13.1) with ESMTP id j2UGJb0w048144 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 30 Mar 2005 18:19:44 +0200 (CEST) (envelope-from ml.diespammer@netfence.it) Received: from netfence.it (xanatar.ventu [10.1.2.6]) (authenticated bits=0) by soth.ventu (8.13.3/8.13.1) with ESMTP id j2UFxJc8084083 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Wed, 30 Mar 2005 17:59:19 +0200 (CEST) (envelope-from ml.diespammer@netfence.it) Message-ID: <424AE8FA.8080306@netfence.it> Date: Wed, 30 Mar 2005 18:59:22 +0100 From: Andrea Venturoli Organization: NetFence User-Agent: Mozilla/5.0 (OS/2; U; Warp 4.5; en-US; rv:1.6) Gecko/20040117 X-Accept-Language: it,en,fr,de MIME-Version: 1.0 To: Kris Kennaway , freebsd-questions@freebsd.org References: <424AACD1.3060802@netfence.it> <20050330134259.GA66640@xor.obsecurity.org> <424ACEF8.60601@netfence.it> <20050330141626.GB73682@xor.obsecurity.org> In-Reply-To: <20050330141626.GB73682@xor.obsecurity.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.45 Subject: Re: mksnap_ffs woes X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 30 Mar 2005 15:59:29 -0000 Kris Kennaway wrote: > It's possible you're seeing deadlock bugs in the snapshot code; you'd > need to compile your system with DDB support and obtain traceback > information as described in the developers' handbook chapter on kernel > debugging. Ok. As soon as I get the chance, I'll do this (I cannot stop a whole network right away). > The snapshot code was intended to support background fsck and that > alone. It's also optionally used by the dump code, but it was not > written as a general-purpose live filesystem snapshot service. Ok. I just think that this, as well as the disclaimer about it being alpha code and the access locks, should be mentioned in the Handbook. Reading that chapter or mksnap_ffs's manual, I didn't get it and I suspect people might get the idea that it is stable code, which provides some functionality that it doesn't. >>Are there other alternatives for live backups? > > Plenty, if you don't demand an instantaneous image of the backup > image. That depends on what you mean for instantaneous... I'll explain my needs briefly: I export (via Samba) a whole bunch of databases that 9 clients read and write. I do not have more details (I didn't write that app myself). The needs are: a) backup data so that in case of severe failure we can get it rapidly back (we are going to loose the last transactions, obviously); b) replicate everything to another machine (via rsync) so that a remote user can see a snapshot of the system status. We probably can live with some incoherent records in a) (after all, something will almost for sure need manual fix anyway); as for b) I fear it might be more prone to problems. So, if for instantaneous you mean at a specific time, I don't care at all wether the image is made an hour earlier or later. All I'd like is coherence. BTW, we have almost no room for changes on the client side :( > The pros and cons of the snapshot code have been discussed on the > mailing lists, and there is a (slightly outdated) information file > here: /usr/src/sys/ufs/ffs/README.snapshot I'm reading all this stuff; I might get back with some more questions later :) bye & Thanks av.