Hi,
I added another disk to my 3-disk raid5 and ran a balance command. After
few hours I looked to output of `fi usage` to see that no data are being
used on the new disk. I got the same result even when balancing my raid5
data or metadata.
Next I tried to convert my raid5 metadata to raid1 (a good idea anyway)
and the new disk started to fill immediately (even though it received
the whole amount of metadata with replicas being spread among the other
drives, instead of being really "balanced". I know why this happened, I
don't like it but I can live with it, let's not go off topic here :)).
Now my usage output looks like this:
# btrfs filesystem usage /mnt/data WARNING: RAID56 detected, not
implemented Overall: Device size: 10.91TiB Device allocated: 316.12GiB
Device unallocated: 10.61TiB Device missing: 0.00B Used: 58.88GiB Free
(estimated): 0.00B (min: 8.00EiB) Data ratio: 0.00 Metadata ratio: 2.00
Global reserve: 512.00MiB (used: 184.94MiB) Data,RAID5: Size:4.59TiB,
Used:4.06TiB /dev/mapper/crypt-sdb 2.29TiB /dev/mapper/crypt-sdc 2.29TiB
/dev/mapper/crypt-sde 2.29TiB Metadata,RAID1: Size:158.00GiB,
Used:29.44GiB /dev/mapper/crypt-sdb 53.00GiB /dev/mapper/crypt-sdc
53.00GiB /dev/mapper/crypt-sdd 158.00GiB /dev/mapper/crypt-sde 52.00GiB
System,RAID1: Size:64.00MiB, Used:528.00KiB /dev/mapper/crypt-sdc
32.00MiB /dev/mapper/crypt-sdd 64.00MiB /dev/mapper/crypt-sde 32.00MiB
Unallocated: /dev/mapper/crypt-sdb 392.04GiB /dev/mapper/crypt-sdc
392.01GiB /dev/mapper/crypt-sdd 2.57TiB /dev/mapper/crypt-sde 393.01GiB
I'm now running `fi balance -dusage=10` (and rising the usage limit). I
can see that the unallocated space is rising as it's freeing the little
used chunks but still no data are being stored on the new disk.
I it some bug? Is `fi usage` not showing me something (as it states
"WARNING: RAID56 detected, not implemented")? Or is there just too much
free space on the first set of disks that the balancing is not bothering
moving any data?
If so, shouldn't it be really balancing (spreading) the data among all
the drives to use all the IOPS capacity, even when the raid5 redundancy
constraint is currently satisfied?
# uname -a Linux keeper 4.19.0-0.bpo.2-amd64 #1 SMP Debian
4.19.16-1~bpo9+1 (2019-02-07) x86_64 GNU/Linux # btrfs --version
btrfs-progs v4.17 # btrfs fi show Label: none uuid:
xxxxxxxxxxxxxxxxxxxxxxxxxx Total devices 4 FS bytes used 4.09TiB devid 2
size 2.73TiB used 2.34TiB path /dev/mapper/crypt-sdc devid 3 size
2.73TiB used 2.34TiB path /dev/mapper/crypt-sdb devid 4 size 2.73TiB
used 2.34TiB path /dev/mapper/crypt-sde devid 5 size 2.73TiB used
158.06GiB path /dev/mapper/crypt-sdd # btrfs fi df . Data, RAID5:
total=4.59TiB, used=4.06TiB System, RAID1: total=64.00MiB,
used=528.00KiB Metadata, RAID1: total=158.00GiB, used=29.43GiB
GlobalReserve, single: total=512.00MiB, used=0.00B
Thanks
Jakub
