Hello Howard,
Thanks for the helpful information! All about the back-mdb sounds so good! Will the new back-mdb included in the next release? Is it recommended to use this backend in production environment?
Thanks for hard work on the great OpenLDAP!
Meike
2011/11/1 Howard Chu hyc@symas.com:
Meike Stone wrote:
Hello,
time ago, we installed a Linux Guest with OpenLDAP (db size appox. 650MByte / ) server in a ESXi environment. Maybe because of a read/write ratio 100:1, the hard discs where heavy used by writing bdb backends memory mapped files. The CPU in that Linux system had iowait (top) between 80% and 100% and the other VMs on the ESXi went slow down.
After changing to shared memory (shm_key), all problems with disc IO where gone.
I read in the mailing list and on "OpenLDAP performance tuning" guide, that it does not matter if using memory mapped files or shared memory until the database is over 8GB. But why we had such problems?
Please note, the OpenLDAP was operating very fast with the memory mapped files, because of using indexes and proper caching.
Now, I want install more than one OpenLDAP server on one Linux system (now real Hardware). Every OpenLDAP server will be bind on a separate IP and DNS host name.
So in this scenario it is hard to calculate the shared memory and assign each LDAP server to the right shared memory region (key).
Therefore I want go back to memory mapped files. Are there any recommendation for sizing the Linux system like: - type of file system (ext3, ext4, xfs, ..) - parameters of file system (syncing -> commit=nrsec, data=*, ... ) - swap using (swappiness, dirty_background_ratio) - ???
Also, back-mdb (in git master) will behave much better in a VM deployment. (Actually, back-mdb behaves better than back-bdb/hdb in all environments.)
-- -- Howard Chu CTO, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/