From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) by finch.gentoo.org (Postfix) with ESMTP id 253B31381FA for ; Tue, 6 May 2014 10:18:51 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id D29ECE0AC4; Tue, 6 May 2014 10:18:43 +0000 (UTC) Received: from mout.gmx.net (mout.gmx.net [212.227.15.15]) (using TLSv1.2 with cipher DHE-RSA-AES256-SHA256 (256/256 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id AB76FE09B4 for ; Tue, 6 May 2014 10:18:42 +0000 (UTC) Received: from marcec ([77.22.138.176]) by mail.gmx.com (mrgmx101) with ESMTPSA (Nemesis) id 0Lpfas-1XMhqI3jnS-00fQZY for ; Tue, 06 May 2014 12:18:40 +0200 Date: Tue, 6 May 2014 12:18:32 +0200 From: Marc Joliet To: gentoo-user@lists.gentoo.org Subject: [gentoo-user] planned btrfs conversion: questions Message-ID: <20140506121832.678ae781@marcec> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.23; x86_64-pc-linux-gnu) 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 MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_/wWxtoMW+Z_rI26+hsUM/Phn"; protocol="application/pgp-signature" X-Provags-ID: V03:K0:VPyvJP8eq1hcCN2YSOS6r+P7pgNYjoobn6NpRH2Jlopfjd3riq1 xbxx2emX2CCCmwoGZ/nCiCdFVO6Uq/l3/ee6QfC3JbpMWERwv0Lp81wIRiLqFxoJrXKZEeg V0s8yXdUzMJWkt+IBDeEKJWXZ88wGeuJS8nYybFhlr3q0p1ShV79Kjynt4LgO7vQqCvwdr+ y4nreX9zjEDstGJ8a1CBw== X-Archives-Salt: 7bd911b8-a2f5-4caa-ab9f-3a7ba44c2676 X-Archives-Hash: 9b897e581172241cee1a34292c644c17 --Sig_/wWxtoMW+Z_rI26+hsUM/Phn Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Hi all, I've become increasingly motivated to convert to btrfs. From what I've see= n, it has become increasingly stable; enough so that it is apparently supposed= to become the default FS on OpenSuse in 13.2. I am motivated by various reasons: - The experience of insignificant data loss after a reboot after no (visible) problems during normal operations (no similar occurrence since)= . I suspect this would have been discovered sooner by btrfs' data checksummin= g. While the data lost was of a small amount, not to mention insignificant (internet pictures) and could be retrieved again easily, I worry that this sort of silent corruption might happen to data that I *do* care about. My backups would become less than useless if I were to discover such corrupt= ion too late. - The outright sexy multiple device support :) . This migration will occur in conjunction with a migration of / + /usr to a cheap SSD that I just bought (Crucial M500 120 GB). The overall plan is thu= s as follows: Replace /boot on /dev/md1 (EXT3, RAID 1) / (with assorted sub-directories, sans /usr) on /dev/md2 (EXT4, RAID 10) the rest on LVM on /dev/md3 (all LVs EXT4, RAID 10) with / + /boot + /usr + swapfile on the SSD (EXT4) the rest (/home, my media partitions) on a btrfs RAID 10 (which replaces an older plan to recreate the RAID 10 + LVM to use the whole disks with the current 1.2 metadata format) The goals are, in addition to alleviating my data safety concerns above, to guarantee that I don't need an initramfs at boot (hence the SSD), and to greatly simplify my partitioning scheme (I just have too many separate logi= cal volumes ;-) ). Any added performance is "just" a nice bonus. The reason why I would choose EXT4 for the SSD is that btrfs still lacks su= pport for swap files and I worry about creating a swap partition on the SSD. Is t= hat warranted, or will the wear-levelling of the SSD handle that just fine? Do = swap partitions support SSDs specially? Also, does anyone know whether EXT4 goes beyond "merely" supporting TRIM? That is, the btrfs wiki advertises the following: "SSD (Flash storage) awareness (TRIM/Discard for reporting free blocks for reuse) and optimizations (e.g. avoiding unnecessary seek optimizations, sending writes in clusters, even if they are from unrelated files. This results in larger write operations and faster write throughput)" Does EXT4 also implement such optimisations for SSDs? So I guess I want to know: does anybody have any further suggestions to mak= e? Is btrfs a good choice for / after all? And should I be using the most rece= nt kernel versions? (I would go with no, despite the advice from upstream, bec= ause the changes in the last two versions don't seem to be particularly user visible, at least to me, from reading kernelnewbies.org.) I also have a more specific question regarding RAID 10: the btrfs wiki says that you can add devices with different sizes to a multiple device setup, b= ut I don't think it says to which RAID levels this applies and how. From [0] I w= ould say it works with RAID 10 (since that's what the example uses), but thought maybe somebody here knows more details and/or gotchas. From my understandin= g, this means that I can iteratively upgrade my RAID 10 to larger drives and h= ave btrfs use all of the available space (or at least as much as is possible). = This is important to me because I currently have 4 320 GB HDDs + 1 (possibly bro= ken, must check) spare and wish to be able to upgrade without having to buy four HDDs at once. Now to the migration plan: first, partition the SSD and copy all relevant f= ile systems to it; this will be done from a Live-CD (SystemRescueCD). After I h= ave configured the mount options appropriately and can boot from that, I should= be able to mount the other file systems (/home and my media partitions) read-o= nly from the actual system and do the RAID + LVM -> btrfs migration from there. Note that I will in general follow the advice from [1-3], and if people recommend btrfs on /, then I will also try to get relevant information from= [4]. [0] https://btrfs.wiki.kernel.org/index.php/SysadminGuide#RAID_and_data_replica= tion [1] https://wiki.archlinux.org/index.php/Solid_State_Drives [2] https://wiki.archlinux.org/index.php/Btrfs [3] http://wiki.gentoo.org/wiki/Btrfs [4] http://wiki.gentoo.org/wiki/Btrfs_system_root Greetings and thanks in advance for any help given --=20 Marc Joliet -- "People who think they know everything really annoy those of us who know we don't" - Bjarne Stroustrup --Sig_/wWxtoMW+Z_rI26+hsUM/Phn Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJTaLb+AAoJEL/Q5oYsiHj0upoP/AonxST/jONz/tnEX8QrWD+p ZI8jff4SeABPnBKnM3n7s9HOBjxy34J0zyBB0J3uP90kLRz9PW9w1zByjL5w/Cc/ aUOEe088Ujk78Z55aGRjHQWwAYfGvVsxwszIaO7Ube6mPMM5zM6KMsDQ6XSmYau2 HScDoqchqgGc6qvdT5dAcmvh9GSCS+v3CIYwIECf63+QOIS+8wKKuA6gFLAFcPX1 VfBpQRT/x7Ut6Mu86Wj7Lw2ZAlf4da+Yra1sW9X9JKzlRxYdCpdiooeZ5F141JCk clnTkkeJFefQxJuddVxFqsJbsfV9oangnBW/LJbYtDIIoGy8XjBhEqetnLv9hPip /Eg4y3jso8RiYFYc0mwvi5NiTwy0uY0Fu+vTDXn22WIbO0RRvaH982IBBcfgql0m mrT89QL+8Pq9DbYofmikTzFKhWiQsgfpexUvvp/VjkvEp8ej4wLu+mfE6t/drHox +A8yWGQroEaMMS5ogBL0Fnhs8Q/btmsgnt+BiqjzQgZ/pyNfkna2b2DNLAirRoGF IH9qfIN7ATRG6JfCcoq+1V2+CikOSGwNUyT56FMjB1c6zKTtsWx19TnAb66TdoJ+ pZ3lssMXl0Ir4VLieIRY03woIVdi6+09wkdkxQag1GGPs2C9cE3+YVpcYTRorMQ6 L5BasmIA7WpEmr8ULg5g =pNrP -----END PGP SIGNATURE----- --Sig_/wWxtoMW+Z_rI26+hsUM/Phn--