Disabling Quotas on NFS file system

On our Cellera NS80, the quotas was activated on some file system and seems that we now reach the soft limit of 4 TB...  So, some users/groups aren't able to save data anymore.  We opened a call with EMC and they replied us to disable quotas if we don't use it.  Which is the case, as we didn't put any quota limit in place, only the 4TB soft limit is now reach ( seems to be the limit in 5.6 ).   Now, we are trying to evaluate the impact of disabling quotas on a FS.  Here is the command we are looking to run :

nas_quotas -off -both -fs    ( repeat this for each file system where quota is activated )

We got 6 file system on which we need to run this command, the largest one got 741 GB of data in it and the smallest got 80GB of data.

We heard that this command is disruptive and we are still trying to figure out how disruptive it is. 

First question, how long this command could take to run ?   I assume not so long as it is a removal of the quota, so no calculation should be required, right ?

Second question, how disruptive this will be ?   Only the file system is affected or the whole NFS service will be temporary unreachable ?

Third question, is there any risk that something blow up/get corrupted when running this command ?  

Our Cellera NS80 expert left, and I'm kind of new to all this, so, was to be carefull before doing anything on the NAS.

Thanks for your help.