With Berkeley DB it&#x27;s even worse, since, by default, BDB uses a memory-mapped <i>file</i> as its cache.  So the cache gets effectively double-managed, first by BDB, then by the OS itself.  This wreaks havoc on performance.<p>The way around this design flaw is to either tell BDB to use SysV shared memory (which really should be the default), or to locate the cache on a ramdisk (e.g. tmpfs on Linux).