[Dovecot] howto disable indexing on dovecot-lda ?

Hello, is it possible to disable indexing on dovecot-lda ?

Right now postfix delivers the mail directly to the nfs server without any problems. If I switch to dovecot-lda the system crashes do to the high I/O and locking. Indexing on lda is not very useful because the number of of imap logins is less than 5% that of incoming mails, so an user could wait for 3 sec to get his mail index, but a new mail can't.

Dovecot version 1.2.15 mail_nfs_storage = yes mail_nfs_index = yes

Than you !