[Dovecot] quick question about fs quota overhead in plugin

Last night I enabled imap_quota so dovecot could report usage reported by disk quota. I don't intend to actually use the quota plugin to place any limits anytime soon though. How much overhead does this add to normal operations that allocate disk space? Ideally I'd like a situation where the only overhead is incurred when the user uses the mail client to specifically check their usage. Is that possible, and/or is there a better way to do this? If it does cause general overhead on the NFS filer, I could just accept it until/unless I feel it becomes a burden I cannot bear.

mail_plugins = acl fts fts_squat quota imap_quota ... quota = fs ...