The
PortalSiteMapProvider class is one of the best performing List data access
methods PortalSiteMapProvider class is going to be most useful if the data you
are retrieving is not significantly different over time. If you are trying to
frequently retrieve different data sets, the PortalSiteMapProvider class will
incur the overhead of constantly reading from the database, inserting data into
the cache and then returning it from the method call The advantage of the
PortalSiteMapProvider class is when it can read data directly from the cache The
amount of memory the PortalSiteMapProvider class has available to use may be
somewhat constrained. It uses the site collection object cache to store data;
by default, the object cache is only 100 megabytes (MB). for More information
on Microsoft performed performance testing against Microsoft® Office SharePoint Server 2007 read this doc
http://office.microsoft.com/download/afile.aspx?AssetID=AM102377231033