One of the biggest changes to OpenLDAP in years has made its way into the latest OpenLDAP 2.4 releases, and that is a brand new backend named “back-mdb”.  This new backend leverages the Lightning Memory-Mapped Database from Symas.  To see why this new backend was introduced, it is useful to look at the differences in performance and resource utilization between old BDB based back-hdb and the new LMDB based back-mdb.

Hardware details

• Dell PowerEdge R710
• 36GB of RAM
• ESXi 5.1 hypervisor
• 2 CPU, 4 cores per CPU, with hyperthreading (16 vCPUs)
• 1.2 TB RAID array from 4x SEAGATE ST9300603SS 300GB 10kRPM drives
• Ubuntu12 64-bit OS (3.5.0-28-generic #48~precise1-Ubuntu SMP kernel)
• LDAP data is stored on its own /ldap partition, using ext2 as the filesystem type
• ext2 options: noatime,defaults

Software details

• OpenLDAP 2.4 Engineering from 5/10/2013
• Berkeley DB 5.2.36 for the back-hdb backend
• For read tests, slamd 2.0.1 was used to…