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
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