Configure btrfs-balance to run out of production times

SUSE Linux Enterprise Server 12 SP5

SUSE Linux Enterprise Server 15 

In general a btrfs balance may have an impact on the systems performance, especially on busy ones or on shared SAN Storage. 
To avoid a balance run during production times systemd offers some very flexible tools to re-schedule the service.

SLES12 SP5 requires a different solution since the btrfsmaintenance tools utilize cron. 
 

SLES15 SP3 and later:
To avoid btrfs balance running during production times let's define a window of 24 hours on Sundays.

Step 1:

sles15sp62:~ # vi /etc/sysconfig/btrfsmaintenance

and change

BTRFS_BALANCE_PERIOD="weekly"

to

BTRFS_BALANCE_PERIOD="Sun *-*-* 00:00:00"

Due to this change, the balance now will always start on Sundays at 00:00 AM. However, it may not be desired to have all systems in a particular environment start at the same time, therefore a random delay is required for the job:

vi /etc/systemd/system/btrfs-balance.timer.d/delay.conf

add

[Timer]
RandomizedDelaySec=86400

The value 86400 has been chosen in this example because a day has 86400 seconds, so the job can run on any time at Sundays. Feel free to adjust as applicable. 
We need to make the changes known to systemd:

systemctl daemon-reload

Please check if the changes have been successfull: 

sles15sp62:~ # systemctl status btrfs-balance.timer
● btrfs-balance.timer - Balance block groups on a btrfs filesystem
     Loaded: loaded (/usr/lib/systemd/system/btrfs-balance.timer; enabled; preset: enabled)
    Drop-In: /etc/systemd/system/btrfs-balance.timer.d
             └─delay.conf, schedule.conf
     Active: active (waiting) since Fri 2025-02-21 09:31:49 CET; 2min 3s ago
    Trigger: Sun 2025-02-23 06:42:42 CET; 1 day 21h left
   Triggers: ● btrfs-balance.service
       Docs: man:btrfs-balance

As already noted SLES 12 SP5 works in a different way:

sles12sp51:~ # vi /etc/sysconfig/btrfsmaintenance

change

BTRFS_BALANCE_PERIOD="weekly"

to

BTRFS_BALANCE_PERIOD="none"

Now create a cron job for the btrfs-balance job via root user simply by running: 

{
    crontab -l
    echo "RANDOM_DELAY=1440"
    echo "0 0  * * SUN /usr/share/btrfsmaintenance/btrfs-balance.sh"
} | crontab - 

Note:

• The behaviour of the variable RANDOM_DELAY in crontabs is described in "man 5 crontab".
• Please note: In opposite to RandomizedDelaySec, the unit of the variable RANDOM_DELAY is given in minutes.
• On SLES 15 SP[X] Make sure that the version of btrfsmaintenance does contain the fix for bcs#1233068:
  

  rpm -q btrfsmaintenance --changelog|grep bsc#1233068
  - Fix for SG#69163, bsc#1233068: