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 A8FFB15815E for ; Fri, 9 Feb 2024 13:03:06 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 107F02BC029; Fri, 9 Feb 2024 13:03:00 +0000 (UTC) Received: from gw1.antarean.org (gw1.antarean.org [194.145.200.214]) by pigeon.gentoo.org (Postfix) with ESMTP id 6BFB22BC014 for ; Fri, 9 Feb 2024 13:02:59 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by gw1.antarean.org (Postfix) with ESMTP id 4TWYtV68lVzyPy for ; Fri, 9 Feb 2024 13:02:58 +0000 (UTC) X-Virus-Scanned: amavisd-new at antarean.org Received: from gw1.antarean.org ([127.0.0.1]) by localhost (gw1.antarean.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id YQTGwT-K-G9i for ; Fri, 9 Feb 2024 13:02:58 +0000 (UTC) Received: from mailstore1.adm.antarean.org (localhost [127.0.0.1]) by gw1.antarean.org (Postfix) with ESMTP id 4TWYtV0f1ZzyP7 for ; Fri, 9 Feb 2024 13:02:58 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mailstore1.adm.antarean.org (Postfix) with ESMTP id 4TWYtT67rDz17 for ; Fri, 9 Feb 2024 13:02:57 +0000 (UTC) X-Virus-Scanned: amavisd-new at antarean.org Received: from mailstore1.adm.antarean.org ([127.0.0.1]) by localhost (mailstore1.adm.antarean.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id QY2Xii-9TchC for ; Fri, 9 Feb 2024 12:57:57 +0000 (UTC) Received: from iris.localnet (iris.adm.antarean.org [10.55.16.47]) by mailstore1.adm.antarean.org (Postfix) with ESMTPA id 4TWYmj41yxz15 for ; Fri, 9 Feb 2024 12:57:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=antarean.org; s=default; t=1707483477; bh=13eWpvnmsJt4GjK+PHPfAyWcruydqRWGlbZW+4fYCSA=; h=From:To:Subject:Date:In-Reply-To:References; b=MFJ8SAgWPyOc/BTCrXgJafIs+gkre9700YHP6eI6euvM68bmbp+MNZvTIHukzRaXy QLWO9zgnDp1uhprzp+0iY8PFuP7xx/0bHC7Qwsr7GgTReJVlFbViSdqlDY0+uz0u6J UIF57PVUPsgmtIyWZSsOQUhU/owv6vSbX4PcjbAQ= From: "J. Roeleveld" To: gentoo-user@lists.gentoo.org Subject: Re: [gentoo-user] Re: Suggestions for backup scheme? Date: Fri, 09 Feb 2024 13:57:57 +0100 Message-ID: <4882577.GXAFRqVoOG@iris> In-Reply-To: References: <4547854.LvFx2qVVIh@iris> 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 MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Archives-Salt: 9550ce56-8a8f-40ec-9213-0f11eda6f8f2 X-Archives-Hash: 53b11d178fec1254579d5387c68d4a6b On Thursday, February 8, 2024 6:44:50 PM CET Wols Lists wrote: > On 08/02/2024 06:38, J. Roeleveld wrote: > > ZFS doesn't have this "max amount of changes", but will happily fill up > > the > > entire pool keeping all versions available. > > But it was easier to add zpool monitoring for this on ZFS then it was to > > add snapshot monitoring to LVM. > > > > I wonder, how do you deal with snapshots getting "full" on your system? > > As far as I'm, concerned, snapshots are read-only once they're created. > But there is a "grow the snapshot as required" option. > > I don't understand it exactly, but what I think happens is when I create > the snapshot it allocates, let's say, 1GB. As I write to the master > copy, it fills up that 1GB with CoW blocks, and the original blocks are > handed over to the backup snapshot. And when that backup snapshot is > full of blocks that have been "overwritten" (or in reality replaced), > lvm just adds another 1GB or whatever I told it to. That works with a single snapshot. But, when I last used LVM like this, I would have multiple snapshots. When I change something on the LV, the original data would be copied to the snapshot. If I would have 2 snapshots for that LV, both would grow at the same time. Or is that changed in recent versions? > So when I delete a snapshot, it just goes through those few blocks, > decrements their use count (if they've been used in multiple snapshots), > and if the use count goes to zero they're handed back to the "empty" pool. I know this is how ZFS snapshots work. But am not convinced LVM snapshots work the same way. > All I have to do is make sure that the sum of my snapshots does not fill > the lv (logical volume). Which in my case is a raid-5. I assume you mean PV (Physical Volume)? I actually ditched the whole idea of raid-5 when drives got bigger than 1TB. I currently use Raid-6 (or specifically RaidZ2, which is the ZFS "equivalent") -- Joost