We are seeing some strange quota limits on OSTs as following:

[root@nmds04 home]# lfs quota -u lect02 -v /root/lustre
Disk quotas for user lect02 (uid 3018):
Filesystem kbytes quota limit grace files quota limit grace
/root/lustre 16 0 1000000000 - 4 0 0 -
lustre4-MDT0000_UUID
4 - 0 - 4 - 0 -
lustre4-OST0000_UUID
0 - 165167900 - - - - -
lustre4-OST0001_UUID
0 - 63031212 - - - - -
lustre4-OST0002_UUID
0 - 53832788 - - - - -
...
lustre4-OST0020_UUID
4* - 4 - - - - -
lustre4-OST0021_UUID
0 - 91758376 - - - - -
...
[root@nmds04 home]# lfs quota -u lect02 -v /root/lustre/ | grep -A1 OST | grep -v OST | awk '

END

'
5572927984

First, some OSTs have much bigger granted limits than their usages. And second, the sum of limits on OSTs exceeds the total limit. What is more, some user which do do have have quota limits can not use more spaces unless the quota is turn off manually.