With the out-of-the-box settings on Linux systems running the ext3 file system, the data is only flushed to disk every five seconds. If the Directory Proxy Server is running on a Linux system using the ext3 file system, consider editing the mount options for that file system to include the following:
This variable changes the flush frequency from five seconds to one second.

You should also set the flush frequency to the /etc/fstab file. Doing the change via the mount command alone will not survive across reboots.