From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ie0-f179.google.com ([209.85.223.179]:44358 "EHLO mail-ie0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757899Ab3FMWvD (ORCPT ); Thu, 13 Jun 2013 18:51:03 -0400 Received: by mail-ie0-f179.google.com with SMTP id c10so19611182ieb.10 for ; Thu, 13 Jun 2013 15:51:02 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20130613212100.GG11290@carfax.org.uk> References: <51BA34EC.1080800@friedels.name> <20130613212100.GG11290@carfax.org.uk> Date: Thu, 13 Jun 2013 16:51:01 -0600 Message-ID: Subject: Re: raid0, raid1, raid5, what to choose? From: cwillu To: Hugo Mills , Hendrik Friedel , linux-btrfs Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Thu, Jun 13, 2013 at 3:21 PM, Hugo Mills wrote: > On Thu, Jun 13, 2013 at 11:09:00PM +0200, Hendrik Friedel wrote: >> Hello, >> >> I'd appreciate your recommendation on this: >> >> I have three hdd with 3TB each. I intend to use them as raid5 eventually. >> currently I use them like this: >> >> # mount|grep sd >> /dev/sda1 on /mnt/Datenplatte type ext4 >> /dev/sdb1 on /mnt/BTRFS/Video type btrfs >> /dev/sdb1 on /mnt/BTRFS/rsnapshot type btrfs >> >> #df -h >> /dev/sda1 2,7T 1,3T 1,3T 51% /mnt/Datenplatte >> /dev/sdb1 5,5T 5,4T 93G 99% /mnt/BTRFS/Video >> /dev/sdb1 5,5T 5,4T 93G 99% /mnt/BTRFS/rsnapshot >> >> Now, what surprises me, and here I lack memory- is that sdb appears >> twice.. I think, I created a raid1, but how can I find out? > > Appearing twice in that list is more an indication that you have > multiple subvolumes -- check the subvol= options in /etc/fstab > >> #/usr/local/smarthome# ~/btrfs/btrfs-progs/btrfs fi show /dev/sdb1 >> Label: none uuid: 989306aa-d291-4752-8477-0baf94f8c42f >> Total devices 2 FS bytes used 2.68TB >> devid 2 size 2.73TB used 2.73TB path /dev/sdc1 >> devid 1 size 2.73TB used 2.73TB path /dev/sdb1 >> >> Now, I wanted to convert it to raid0, because I lack space and >> redundancy is not important for the Videos and the Backup, but this >> fails: >> ~/btrfs/btrfs-progs/btrfs fi balance start -dconvert=raid0 /mnt/BTRFS/ >> ERROR: error during balancing '/mnt/BTRFS/' - Inappropriate ioctl for device > > /mnt/BTRFS isn't a btrfs subvol, according to what you have listed > above. It's a subdirectory in /mnt which is contains two subdirs > (Video and rsnapshot) which are used as mountpoints for subvolumes. > > Try running the above command with /mnt/BTRFS/Video instead (or > rsnapshot -- it doesn't matter which). > >> dmesg does not help here. >> >> Anyway: This gave me some time to think about this. In fact, as soon >> as raid5 is stable, I want to have all three as a raid5. Will this >> be possible with a balance command? If so: will this be possible as >> soon as raid5 is stable, or will I have to wait longer? > > Yes, it's possible to convert to RAID-5 right now -- although the > code's not settled down into its final form quite yet. Note that > RAID-5 over two devices won't give you any space benefits over RAID-1 > over two devices. (Or any reliability benefits either). > > Hugo. > > -- > === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === > PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk > --- "Are you the man who rules the Universe?" "Well, I --- > try not to." Raid5 currently is only suitable for testing: it's known and expected to break on power cuts, for instance. The parity logging stuff is waiting on the skip-list implementation you may have read about on lwn, otherwise the performance overhead wasn't acceptable or some such.