On Mon, Jan 2, 2017 at 4:25 AM, Jens Dueholm Christensen <JEDC@xxxxxxxxxxx> wrote:
On Friday, December 30, 2016 07:05 PM Brian Andrus wrote:
> We have a set it and forget it cronjob setup once an hour to keep things a bit more balanced.
>
> 1 * * * * /bin/bash /home/briana/reweight_osd.sh 2>&1 | /usr/bin/logger -t ceph_reweight
>
> The script checks and makes sure cluster health is OK and no other rebalancing is going on. It will
> also check the reported STDDEV from `ceph osd df` and if outside acceptable ranges executes a
> gentle reweight.
Would you mind sharing that script?
The script attached is a quick and dirty bash script, not perfect, blah blah blah... consider it still under development but feel free to use it as a base for your own environment needs.
> The three parameters after the reweight-by-utilization are not well documented, but they are
>
> 103 - Select OSDs that are 3% above the average (default is 120 but we want a larger pool of OSDs to
choose from to get an eventual tighter tolerance)
> .010 - don't reweight any OSD more than this increment (keeps the impact low)
> 10 - number of OSDs to select (to keep impact manageable)
Ah! Thank you for that pointer.
For the record the same arguments can be used for dry-runs of "ceph osd test-reweight-by-utilization ..."
and correspond to these values in the output from test-reweight-by-utilization:
oload 120
max_change 0.05
max_change_osds 4
The above values are the current defaults in Hammer (0.94.9), but can easily be changed to see the impact
before running the actual rebalance..
Regards,
Jens Dueholm Christensen
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Brian Andrus
Cloud Systems Engineer
DreamHost, LLC
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