Getting the best performance of an LDAP directory server is a difficult task as there are many parameters to take into account, especially with the hardware itself. The CPU clock matters for processing thousands of requests per second as fast as possible. The amount of memory controls how much caching can be done for optimization. The storage subsystem has has some importance on both read and write operations, both in term of throughput and response time. The network interfaces sets how fast to read and respond to client applications.
But the filesystem and how it is configured is also proven to be part of the equation.
Brad Diggs, aka “The Zone Manager” and Senior Directory Architect,has posted a long, detailed and extremely well written article on Filesystem cache optimization strategies, comparing UFS and ZFS, providing tuning tips for both of them.
To quote one of my co-worker:
“after I applied some of those changes, we went from 850 modifications per second to 1100 modifications per second, but more importantly the variation was drastically reduced, providing more constant performance”.