From owner-freebsd-questions@FreeBSD.ORG Wed Jul 30 10:03:05 2008 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id A04491065692 for ; Wed, 30 Jul 2008 10:03:05 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from smtp.infracaninophile.co.uk (gate6.infracaninophile.co.uk [IPv6:2001:8b0:151:1::1]) by mx1.freebsd.org (Postfix) with ESMTP id 1D8B98FC12 for ; Wed, 30 Jul 2008 10:03:04 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from happy-idiot-talk.infracaninophile.co.uk (localhost [IPv6:::1]) (authenticated bits=0) by smtp.infracaninophile.co.uk (8.14.2/8.14.2) with ESMTP id m6UA2xFO092135; Wed, 30 Jul 2008 11:02:59 +0100 (BST) (envelope-from m.seaman@infracaninophile.co.uk) X-DKIM: Sendmail DKIM Filter v2.7.0 smtp.infracaninophile.co.uk m6UA2xFO092135 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=infracaninophile.co.uk; s=200708; t=1217412179; bh=KGWjtIBHUmuduy 0t6Jb6FC1xrOl/dHpsjlt+A9tM9so=; h=Message-ID:Date:From:MIME-Version: To:CC:Subject:References:In-Reply-To:Content-Type:Cc:Content-Type: Date:From:In-Reply-To:Message-ID:Mime-Version:References:To; z=Mes sage-ID:=20<48903C4C.2090902@infracaninophile.co.uk>|Date:=20Wed,=2 030=20Jul=202008=2011:02:52=20+0100|From:=20Matthew=20Seaman=20|Organization:=20Infracaninophile|User -Agent:=20Thunderbird=202.0.0.16=20(X11/20080726)|MIME-Version:=201 .0|To:=20Modulok=20|CC:=20freebsd-questions@free bsd.org|Subject:=20Re:=20dumping=20mounted=20file=20systems=20with= 20insufficient=20space...|References:=20<64c038660807300154ue4e5a0c yb792b46fd3ec6037@mail.gmail.com>|In-Reply-To:=20<64c03866080730015 4ue4e5a0cyb792b46fd3ec6037@mail.gmail.com>|X-Enigmail-Version:=200. 95.6|Content-Type:=20multipart/signed=3B=20micalg=3Dpgp-sha256=3B=0 D=0A=20protocol=3D"application/pgp-signature"=3B=0D=0A=20boundary=3 D"------------enigF7867D4E2875AEA7FA27DBBD"; b=1aFuPbebMA95N2Agvjku RH4vO1eIY8eJ3pAhZuS7rAil89Pdp/OcL8YdS8oHOhWzzTplKJ+pah/TUch6ZgeJbur V7Ch+ZYCC4vPe6E8YmN9CNCAhxdaIaQ4nihYNpIqZMgfwBxAqCfVTAMgplaCEqpiv8f sYElQgdxq1FV0Q2+I= Message-ID: <48903C4C.2090902@infracaninophile.co.uk> Date: Wed, 30 Jul 2008 11:02:52 +0100 From: Matthew Seaman Organization: Infracaninophile User-Agent: Thunderbird 2.0.0.16 (X11/20080726) MIME-Version: 1.0 To: Modulok References: <64c038660807300154ue4e5a0cyb792b46fd3ec6037@mail.gmail.com> In-Reply-To: <64c038660807300154ue4e5a0cyb792b46fd3ec6037@mail.gmail.com> X-Enigmail-Version: 0.95.6 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enigF7867D4E2875AEA7FA27DBBD" X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.0 (smtp.infracaninophile.co.uk [IPv6:::1]); Wed, 30 Jul 2008 11:02:59 +0100 (BST) X-Virus-Scanned: ClamAV 0.93.3/7888/Wed Jul 30 08:23:13 2008 on happy-idiot-talk.infracaninophile.co.uk X-Virus-Status: Clean X-Spam-Status: No, score=-3.0 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VERIFIED,NO_RELAYS autolearn=ham version=3.2.5 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on happy-idiot-talk.infracaninophile.co.uk Cc: freebsd-questions@freebsd.org Subject: Re: dumping mounted file systems with insufficient space... 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: Wed, 30 Jul 2008 10:03:05 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigF7867D4E2875AEA7FA27DBBD Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Modulok wrote: > Before I try this on a live server... >=20 > I can use dump(8) an active, mounted file systems via the -L flag. > According to the manual, this first creates a snapshot of the file > system, to the .snap directory of the file systems root. What if the > file system to be dumped, does not have sufficient free-space to store > a snapshot? Can I still safely dump(8) a mounted file system? A snapshot doesn't take any significant /extra/ space itself. Rather it = consists of marking the state of the system at that time and provides a view (via the .snap directory) of that state of the filesystem. Of cours= e,=20 subsequent modifications of the filesystem can cause more space than=20 otherwise expected to be used up -- as both the snapshot and the latest=20 versions of anything have to be kept around -- but how much impact this h= as=20 depends entirely on the IO traffic characteristics of your particular=20 filesystem and cannot be predicted in any useful fashion without a great deal more information. If snapshots won't work for you, another trick (if you can swing it) is t= o=20 have the data on a RAID1 mirror. Then you can detach one of the mirrors,= =20 back it up and then reattach the mirror. Doing this with gmirror is a simple matter of writing about a 10 line shell script. Other mirroring=20 hard/soft-ware may be less cooperative. However you do it, this will involve an extended period while mirrors resynchronise after the backup where your file system won't have the desired level of resilience. If you can't use snapshots, can't split the mirror and you can't unmount the filesystem, then the next best thing is to make the filesystem as=20 quiescent as possible. Basically, shut down any processes using the=20 filesystem. That's probably as unacceptable as any of the other alternatives -- in which case, you can still go ahead and dump the=20 filesystem, but don't expect the generated dump to be 100% consistent.=20 It will be 'good enough' for some purposes, but files actively involved in IO at the time the dump is made are likely to be corrupted. =20 Cheers, Matthew --=20 Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard Flat 3 PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate Kent, CT11 9PW --------------enigF7867D4E2875AEA7FA27DBBD Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEAREIAAYFAkiQPFMACgkQ8Mjk52CukIyIhQCfQI3HgoJnQFf5yUtdtPOTJcJ9 iVMAn2etwcDxCF7dqxUA0SNr6TCqCU2i =c048 -----END PGP SIGNATURE----- --------------enigF7867D4E2875AEA7FA27DBBD--