From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mari.romanrm.net ([157.7.203.202]:37178 "EHLO mari.romanrm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751376AbaGRNFb (ORCPT ); Fri, 18 Jul 2014 09:05:31 -0400 Date: Fri, 18 Jul 2014 19:05:24 +0600 From: Roman Mamedov To: Duncan <1i5t5.duncan@cox.net> Cc: linux-btrfs@vger.kernel.org Subject: Re: Questions on incremental backups Message-ID: <20140718190524.143439e1@natsu> In-Reply-To: <20140718053422.78784982@ws> References: <1405627978.2630.39.camel@s-Air> <20140718053422.78784982@ws> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/WiVpGdKG6Q7RppV3SNxO4cD"; protocol="application/pgp-signature" Sender: linux-btrfs-owner@vger.kernel.org List-ID: --Sig_/WiVpGdKG6Q7RppV3SNxO4cD Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Fri, 18 Jul 2014 05:34:22 -0700 Duncan <1i5t5.duncan@cox.net> wrote: > Effectively, admins can choose NOCOW XOR frequent-snapshotting, altho > the fact that snapshots stop at subvolume borders can be used as a > partial workaround, by putting NOCOW files on a dedicated partition and > not snapshotting it, exactly as I mentioned. You can't backup running VM images and datafiles of an active database using "traditional" backup techniques such as file copy or rsync. The tail of a f= ile you're copying for a backup will be long-inconsistent with the overall state or the head of the file when you started copying. Snapshots on the other ha= nd are atomic, and can very much be used to create a static copy of the files = for the purposes of compressing/copying away somewhere. And at worst, the "restored from backup" state of such a backed up VM or DB will be equivalent to it just having had a power-loss. Journalling FSes and databases can deal with that with no major problems. So just exercise moderation, snapshot e.g. once an hour or even a day, the result will still be better than not using NOCOW, and will deliver most of = the benefits you get by snapshotting. Another option is to snapshot->backup->delete snapshot. --=20 With respect, Roman --Sig_/WiVpGdKG6Q7RppV3SNxO4cD Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAlPJG5QACgkQTLKSvz+PZwgZTwCfdEgpiCZ63LOhVQfRtQfCrOKo M7cAn1p1L6izOkE38N8JXqy5O/8HG9s8 =fxzo -----END PGP SIGNATURE----- --Sig_/WiVpGdKG6Q7RppV3SNxO4cD--