This has been a request to the GlusterFS developers for a while now and there is nothing out-of-the-box solution you can use. However, with a few scripts it’s not impossible.
Pretty much entire Gluster system is managed by a single gluster command and with a few options, you can write yourself health monitoring scripts. See here for listing info on bricks and volumes — http://gluster.org/community/documentation/index.php/Gluster_3.2:_Displaying_Volume_Information
To monitor performance, look at this link — http://gluster.org/community/documentation/index.php/Gluster_3.2:_Monitoring_your_GlusterFS_Workload
UPDATE: Do consider upgrading to http://gluster.org/community/documentation/index.php/About_GlusterFS_3.3
You are always better off with being on the latest release since they seem to have more bug fixes and well supported. Ofcourse, run your own tests before moving to a newer release — http://vbellur.wordpress.com/2012/05/31/upgrading-to-glusterfs-3-3/ 🙂
There is an admin guide with specific section for monitoring your GlusterFS 3.3 installation in Chapter 10 — http://www.gluster.org/wp-content/uploads/2012/05/Gluster_File_System-3.3.0-Administration_Guide-en-US.pdf
See here for another nagios script — http://code.google.com/p/glusterfs-status/