maildir very dirty sync option

Hello ,

I have an active passive dovecot setup with glusterfs as a mail storage and using maildirs, we used to have a problem when users with large mailboxes sync their folders. This caused the load average to increase in the server , after a while we have enabled the very_dirty_sync option in dovecot , things got better and the problem disappeared but we need to know if there is any thing else that we need to do or know about the very_dirty_sync option that may cause future problems .

Thanks in advance