I was partially wrong; this is what Mike McCandless (Lucene-in-Action, 2nd edition) explained at Manning forum:
mergeFactor of 1000 means you will have up to 1000 segments at each level. A level 0 segment means it was flushed directly by IndexWriter. After you have 1000 such segments, they are merged into a single level 1 segment. Once you have 1000 level 1 segments, they are merged into a single level 2 segment, etc. So, depending on how many docs you add to your index, you'll could have 1000s of segments w/ mergeFactor=1000. http://www.manning-sandbox.com/thread.jspa?threadID=33784&tstart=0 So, in case of mergeFactor=100 you may have (theoretically) 1000 segments, 10-20 files each (depending on schema)... mergeFactor=10 is default setting... ramBufferSizeMB=1024 means that you need at least double Java heap, but you have -Xmx1024m... -Fuad > > I am getting too many open files error. > > Usually I test on a server that has 4GB RAM and assigned 1GB for > tomcat(set JAVA_OPTS=-Xms256m -Xmx1024m), ulimit -n is 256 for this > server and has following setting for SolrConfig.xml > > > > <useCompoundFile>true</useCompoundFile> > > <ramBufferSizeMB>1024</ramBufferSizeMB> > > <mergeFactor>100</mergeFactor> > > <maxMergeDocs>2147483647</maxMergeDocs> > > <maxFieldLength>10000</maxFieldLength> >
