This repo contains some python scripts to work with python. Script has dependensies on each other, so repo have to cloned, you can't just grub and run selected scripts.

$ git clone https://github.com/koder-ua/ceph-tools.git
$ cd ceph-tools
$ pip install -r requirements.txt

rebalance.py

This script allows to gently change a weight of set of OSD by increasing/decreasing it with small step and wait till rebalance complete.

To run it ones need to create yaml file, describing expected weights of OSD's. Example:

step: 0.1  # max weight change in one step for one OSD
restep: 0.02  # max reweight change in one step for one OSD
max_updated_nodes: 4   # max OSD, updated in parallel
min_weight_diff: 0.01  # minimal weight change to be applied
                       # e.g. if current weight is 1.222 and required weight is 1.223 weight would not be changed
min_reweight_diff: 0.01  # minimal reweight change to be applied, same as above
osds:   # list of OSD
    # root/host/name - path in CRUSH to select osd
  - osd: osd.0
    root: default 
    host: osd-0
    weight: 0.3  # new weight
    reweight: 0.95  # new reweight
  - osd: osd.1
    root: default
    host: osd-2
    weight: 0.3
  - osd: osd.2
    root: default
    host: osd-1
    weight: 0.3
    
  # For reweight change - be aware that osd can't have different reweight in different subtree's
  - osd: osd.2
    reweight: 0.95
  - osd: osd.122
    reweight: 0.9

Estimate how many data would be moved during rebalance:

$ python rebalance.py -q -e rebalance.yaml
    Total bytes to be moved : 2.2 GiB
    Total PG to be moved  : 71

Run rebalance:

$ python rebalance.py rebalance.yaml 
    
    root=default/host=ceph-osd0/osd=osd.0 weight = 0.018 => 0.2
    root=default/host=ceph-osd1/osd=osd.1 weight = 0.018 => 0.2
    root=default/host=ceph-osd3/osd=osd.2 weight = 0.018 => 0.2
    root=default/host=ceph-osd2/osd=osd.3 weight = 0.018 => 0.2
    Total sum of all weight changes 0.8
    Total bytes to be moved : 2.0 GiB
    Total PG to be moved  : 63
    Waiting for cluster to complete rebalance done
    ceph osd crush set osd.0 0.499979 root=default host=osd-0
    Waiting for cluster to complete rebalance done
    Done 12%
    ceph osd crush set osd.1 0.2 root=default host=osd-2
    ....

You can stop tool at any time and then start again - it will continue from where it finished.