Ceph

reweight-by-utilization command along with the decreasing the overutilized osds it will also increase the weight of underutilized, But while choosing the underutilized there is a small glitch reweight-by-utilization works on a sorted list from higher to lower utilized osds.

for ex assume utilization list looks like [0.80, 0.75,0.71, 0.60, 0.55,0.45,0.30] and assume avg_utilization=0.60 and max_osd=4. Now assume there are 2 osds which satisfy oload values and it will be picked for decreasing the weight, since max_osd is 4 we can choose 2 more osds for increasing the weight.

While walking in this list first osd with utilization of 0.55(which is less than 0.60) will be considered as underutilized and thereby its weight will be increased. Instead we can pick the osd with 0.30 utilization since its the most underutilized osd.