From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by finch.gentoo.org (Postfix) with ESMTPS id 55F6A15815E for ; Sun, 4 Feb 2024 15:49:03 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 4365C2BC024; Sun, 4 Feb 2024 15:48:57 +0000 (UTC) Received: from ciao.gmane.io (ciao.gmane.io [116.202.254.214]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id DFFCE2BC015 for ; Sun, 4 Feb 2024 15:48:56 +0000 (UTC) Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1rWejl-0006hW-9x for gentoo-user@lists.gentoo.org; Sun, 04 Feb 2024 16:48:53 +0100 X-Injected-Via-Gmane: http://gmane.org/ To: gentoo-user@lists.gentoo.org From: Grant Edwards Subject: [gentoo-user] Re: Suggestions for backup scheme? Date: Sun, 4 Feb 2024 15:48:44 -0000 (UTC) Message-ID: References: <8f5371a5-07af-456e-8517-cb9bb664fac4@youngman.org.uk> <17a2d820-4745-405d-844a-09e27184e56a@youngman.org.uk> User-Agent: slrn/1.0.3 (Linux) Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org X-Auto-Response-Suppress: DR, RN, NRN, OOF, AutoReply X-Archives-Salt: 22238427-d3c1-4b5c-9a9f-a04c0fcf8c6e X-Archives-Hash: fc7cead1100c6596e1c91555add12d26 On 2024-02-04, Wols Lists wrote: > On 04/02/2024 06:24, Grant Edwards wrote: > >> I don't understand, are you saying that somehow your backup doesn't >> contain a copy of every file? >> > YES! Let's make it clear though, we're talking about EVERY VERSION of > every backed up file. > And you need to get your head round the fact I'm not - actually - > backing up my filesystem. I'm actually snapshoting my disk volume, my > disk partition if you like. OK I see. That's a bit different than what I'm doing. I'm backing up a specific set of directory trees from a couple different filesystems. There are large portions of the "source" filesystems that I have no need to back up. And within those directory trees that do get backed up there are also some excluded subtrees. > Your strategy contains a copy of every file in your original backup, a > full copy of the file structure for every snapshot, and a full copy of > every version of every file that's been changed. Right. > My version contains a complete copy of the current backup and > (thanks to the magic of lvm) a block level diff of every snapshot, > which appears to the system as a complete backup, despite taking up > much less space than your typical incremental backup. If I were backing up entire filesystems, I can see how that would definitely be true. > To change analogies completely - think git. My lvm snapshot is like > a git commit. Git only stores the current HEAD, and retrieves > previous commits by applying diffs. If I "check out a backup" (ie > mount a backup volume), lvm applies a diff to the live filesystem. Got it, thanks.