On Tue, Nov 1, 2011 at 6:43 PM, Howard Chu <[email protected]> wrote: > 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). >> > > ?? Just pick some key numbers that are spread out "enough" to not overlap. > 10, 20, 30, 40, etc. > > > 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) >> - ??? >> > > Probably the most important setting is to mount with noatime or relatime. > > Disabling write barrier is a big win and ext4 or perhaps xfs is a good choice (http://www.ep.ph.bham.ac.uk/general/support/raid/raidperf11.html).
hth > -- > -- Howard Chu > CTO, Symas Corp. http://www.symas.com > Director, Highland Sun http://highlandsun.com/hyc/ > Chief Architect, OpenLDAP > http://www.openldap.org/**project/<http://www.openldap.org/project/> > >
