From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Helmut Hullen" Subject: Re: "not enough space" with "data raid0" Date: 17 Mar 2012 14:46:00 +0100 Message-ID: References: <20120317122522.GD3172@carfax.org.uk> Reply-To: helmut@hullen.de Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII To: linux-btrfs@vger.kernel.org Return-path: In-Reply-To: <20120317122522.GD3172@carfax.org.uk> List-ID: Hallo, Hugo, Du meintest am 17.03.12: [no space left on device ...] >>> Where is the problem, how can I use the full space? >> Effectively it's missing the trigger to rebalance when the 'primary' >> device starts to get full, or just to randomly spread the data >> between the devices. > No, a balance isn't going to help here. RAID-0 requires a minimum > of 2 chunks in a block group. With two disks, you're only going to be > able to fill the smallest one before you run out of space. Ok - it happens only with 2 disks/Partitions? I've continued playing; added a 3rd partition/device and then balanced: # btrfs device add /dev/sdd1 /mnt/btr ## 73 + 146 + 146 GByte # df Filesystem 1K-blocks Used Available Use% Mounted on /dev/sdc1 358432300 225400136 59842800 80% /mnt/btr # added about 70 GByte (all together more than 3 times the smallest partition) # btrfs fi show Label: 'Scsi' uuid: e30586e9-a903-4d17-8ec0-1781457212c6 Total devices 3 FS bytes used 214.67GB devid 1 size 68.37GB used 68.37GB path /dev/sdb1 devid 3 size 136.73GB used 41.01GB path /dev/sdd1 devid 2 size 136.73GB used 109.36GB path /dev/sdc1 Btrfs Btrfs v0.19 # btrfs fi df /mnt/btr Data, RAID0: total=216.71GB, used=214.38GB System, RAID1: total=8.00MB, used=24.00KB System: total=4.00MB, used=0.00 Metadata, RAID1: total=1.00GB, used=295.13MB ================================================================= # btrfs fi balance /mnt/btr # btrfs fi show Label: 'Scsi' uuid: e30586e9-a903-4d17-8ec0-1781457212c6 Total devices 3 FS bytes used 214.67GB devid 1 size 68.37GB used 67.34GB path /dev/sdb1 devid 3 size 136.73GB used 40.85GB path /dev/sdd1 devid 2 size 136.73GB used 107.85GB path /dev/sdc1 Btrfs Btrfs v0.19 # btrfs fi df /mnt/btr Data, RAID0: total=215.01GB, used=214.38GB System, RAID1: total=8.00MB, used=24.00KB System: total=4.00MB, used=0.00 Metadata, RAID1: total=512.00MB, used=294.88MB ---------------------------------------------------------------------- Looks as desired, the 3-disks-system contains more than 3 times the smallest disk. Balancing hasn't redistributed the contents - no problem. By the way: you should name the prefixes in the NIST way for powers of 2: KiB, MiB, GiB. Or change to decimal prefixes. Viele Gruesse! Helmut