Quick topic for users like me who want to save/snapshot there indices on NFS Storage !
Generaly we got permission issue "AccessDenied" returned by logs.
So to overwrite or bypass as you want, you could do some
setfacl -Rdm g:<elk_group>:rwx <save_dir>
In the futur, any folder/files created in your NFS share will be overwrited by the good permission !
Hope this help some of you.