Re: Balance of Raid1 pool, does not balance properly.

[Peter Becker <floyd.net@gmail.com>]

for the future you can create a little cron script to avoid this issue.
the data distribution should then be more regular, even if you delete
or overwrite a lot.

deppend on your workload use the right :

# cron.daily / cron.weekly
btrfs balance start -musage=0 -dusage=0 # releases empty blocks for
more unallocated space with can used by future balance runs
btrfs balance start -musage=25 -dusage=25
btrfs balance start -musage=50 -dusage=50


# cron.weekly / cron.monthly
btrfs balance start -musage=90 -dusage=90

A full balance run is then only needed if you add a new device to the
pool or replace a device with a bigger one.


if you are more interesseted about the block usage of your current fs
you can use this little script:

cd /tmp
wget https://raw.githubusercontent.com/kdave/btrfs-progs/master/btrfs-debugfs
chmod +x btrfs-debugfs
stats=$(sudo ./btrfs-debugfs -b /)

echo "00-49: " $(echo "$stats" | grep "usage 0.[0-4]" -c)
echo "50-79: " $(echo "$stats" | grep "usage 0.[5-7]" -c)
echo "80-89: " $(echo "$stats" | grep "usage 0.8" -c)
echo "90-99: " $(echo "$stats" | grep "usage 0.9" -c)
echo "100:   " $(echo "$stats" | grep "usage 1." -c)

The btrfs-debugfs script is from the btrfs progs source and report the
usage of each block group. The following script groups the result.

This script should take less than a few minutes to complete.

Or you can use btrfs-headmap with create a picture:
https://github.com/knorrie/btrfs-heatmap

Am Do., 10. Jan. 2019 um 19:21 Uhr schrieb Karsten Vinding
<karstenvinding@gmail.com>:
>
> Thanks for the answer.
>
> I had already tried "
>
> btrfs balance start -musage=75 -dusage=75 /mnt
>
> It only reallocated 3 blocks.
>
> But after I had moved some data, I ran it with 90, and it realocated a lot more.
>
> I have a new balance running, and this time it seems to be doing its job. At least data is distributed more evenly across disks.
>
> Its not done yet, but its looking fine.
>
>