Hi, Uwe
  Thanks for your timely reply. Yes,  those documents are huge text. We
have ten indices, and each of them has approximate 75G index size on disk.
Following is the directory  content of one of the indices.

Thanks & Best Regards!
lubin

total 74G
-rw-r--r-- 1 root root  100K Jan 10 16:11 _2ncr_4k.del
-rw-r--r-- 1 root root  1.1G Aug  4 12:52 _2ncr.fdt
-rw-r--r-- 1 root root  468K Aug  4 12:52 _2ncr.fdx
-rw-r--r-- 1 root root  636K Aug  4 12:55 _2ncr.fnm
-rw-r--r-- 1 root root  398M Aug  4 12:53 _2ncr_Lucene41_0.doc
-rw-r--r-- 1 root root  712M Aug  4 12:53 _2ncr_Lucene41_0.pay
-rw-r--r-- 1 root root  744M Aug  4 12:53 _2ncr_Lucene41_0.pos
-rw-r--r-- 1 root root  129M Aug  4 12:53 _2ncr_Lucene41_0.tim
-rw-r--r-- 1 root root  3.1M Aug  4 12:53 _2ncr_Lucene41_0.tip
-rw-r--r-- 1 root root  822M Aug  4 12:54 _2ncr_Lucene45_0.dvd
-rw-r--r-- 1 root root  210K Aug  4 12:54 _2ncr_Lucene45_0.dvm
-rw-r--r-- 1 root root   540 Aug  4 12:55 _2ncr.si
-rw-r--r-- 1 root root  1.5G Aug  4 12:55 _2ncr.tvd
-rw-r--r-- 1 root root  441K Aug  4 12:55 _2ncr.tvx
-rw-r--r-- 1 root root   98K Jan 11 11:43 _555c_5x.del
-rw-r--r-- 1 root root  1.1G Aug 25 12:51 _555c.fdt
-rw-r--r-- 1 root root  457K Aug 25 12:51 _555c.fdx
-rw-r--r-- 1 root root  872K Aug 25 12:54 _555c.fnm
-rw-r--r-- 1 root root  389M Aug 25 12:52 _555c_Lucene41_0.doc
-rw-r--r-- 1 root root  713M Aug 25 12:52 _555c_Lucene41_0.pay
-rw-r--r-- 1 root root  750M Aug 25 12:52 _555c_Lucene41_0.pos
-rw-r--r-- 1 root root  136M Aug 25 12:52 _555c_Lucene41_0.tim
-rw-r--r-- 1 root root  3.2M Aug 25 12:52 _555c_Lucene41_0.tip
-rw-r--r-- 1 root root  1.1G Aug 25 12:53 _555c_Lucene45_0.dvd
-rw-r--r-- 1 root root  442K Aug 25 12:53 _555c_Lucene45_0.dvm
-rw-r--r-- 1 root root   540 Aug 25 12:54 _555c.si
-rw-r--r-- 1 root root  1.4G Aug 25 12:54 _555c.tvd
-rw-r--r-- 1 root root  422K Aug 25 12:54 _555c.tvx
-rw-r--r-- 1 root root   93K Jan 10 16:38 _790n_5s.del
-rw-r--r-- 1 root root  1.1G Sep  6 14:17 _790n.fdt
-rw-r--r-- 1 root root  438K Sep  6 14:17 _790n.fdx
-rw-r--r-- 1 root root  1.1M Sep  6 14:20 _790n.fnm
-rw-r--r-- 1 root root  380M Sep  6 14:18 _790n_Lucene41_0.doc
-rw-r--r-- 1 root root  684M Sep  6 14:18 _790n_Lucene41_0.pay
-rw-r--r-- 1 root root  746M Sep  6 14:18 _790n_Lucene41_0.pos
-rw-r--r-- 1 root root  141M Sep  6 14:18 _790n_Lucene41_0.tim
-rw-r--r-- 1 root root  3.5M Sep  6 14:18 _790n_Lucene41_0.tip
-rw-r--r-- 1 root root  1.2G Sep  6 14:20 _790n_Lucene45_0.dvd
-rw-r--r-- 1 root root  550K Sep  6 14:20 _790n_Lucene45_0.dvm
-rw-r--r-- 1 root root   540 Sep  6 14:20 _790n.si
-rw-r--r-- 1 root root  1.4G Sep  6 14:20 _790n.tvd
-rw-r--r-- 1 root root  412K Sep  6 14:20 _790n.tvx
-rw-r--r-- 1 root root   82K Jan 10 16:38 _bv18_8d.del
-rw-r--r-- 1 root root  1.1G Oct 10 12:17 _bv18.fdt
-rw-r--r-- 1 root root  425K Oct 10 12:17 _bv18.fdx
-rw-r--r-- 1 root root  1.4M Oct 10 12:20 _bv18.fnm
-rw-r--r-- 1 root root  363M Oct 10 12:18 _bv18_Lucene41_0.doc
-rw-r--r-- 1 root root  622M Oct 10 12:18 _bv18_Lucene41_0.pay
-rw-r--r-- 1 root root  728M Oct 10 12:18 _bv18_Lucene41_0.pos
-rw-r--r-- 1 root root  133M Oct 10 12:18 _bv18_Lucene41_0.tim
-rw-r--r-- 1 root root  3.4M Oct 10 12:18 _bv18_Lucene41_0.tip
-rw-r--r-- 1 root root  1.9G Oct 10 12:20 _bv18_Lucene45_0.dvd
-rw-r--r-- 1 root root  724K Oct 10 12:20 _bv18_Lucene45_0.dvm
-rw-r--r-- 1 root root   540 Oct 10 12:20 _bv18.si
-rw-r--r-- 1 root root  1.3G Oct 10 12:20 _bv18.tvd
-rw-r--r-- 1 root root  380K Oct 10 12:20 _bv18.tvx
-rw-r--r-- 1 root root   36K Jan 10 16:11 _c1uj_4k.del
-rw-r--r-- 1 root root  650M Oct 10 22:42 _c1uj.fdt
-rw-r--r-- 1 root root  227K Oct 10 22:42 _c1uj.fdx
-rw-r--r-- 1 root root  1.3M Oct 10 22:43 _c1uj.fnm
-rw-r--r-- 1 root root  177M Oct 10 22:42 _c1uj_Lucene41_0.doc
-rw-r--r-- 1 root root  412M Oct 10 22:42 _c1uj_Lucene41_0.pay
-rw-r--r-- 1 root root  428M Oct 10 22:42 _c1uj_Lucene41_0.pos
-rw-r--r-- 1 root root   54M Oct 10 22:42 _c1uj_Lucene41_0.tim
-rw-r--r-- 1 root root  1.6M Oct 10 22:42 _c1uj_Lucene41_0.tip
-rw-r--r-- 1 root root  385M Oct 10 22:43 _c1uj_Lucene45_0.dvd
-rw-r--r-- 1 root root  390K Oct 10 22:43 _c1uj_Lucene45_0.dvm
-rw-r--r-- 1 root root   540 Oct 10 22:43 _c1uj.si
-rw-r--r-- 1 root root  776M Oct 10 22:43 _c1uj.tvd
-rw-r--r-- 1 root root  173K Oct 10 22:43 _c1uj.tvx
-rw-r--r-- 1 root root   64K Jan 10 16:11 _dz32_75.del
-rw-r--r-- 1 root root  1.1G Oct 21 02:30 _dz32.fdt
-rw-r--r-- 1 root root  415K Oct 21 02:30 _dz32.fdx
-rw-r--r-- 1 root root  1.6M Oct 21 02:34 _dz32.fnm
-rw-r--r-- 1 root root  313M Oct 21 02:31 _dz32_Lucene41_0.doc
-rw-r--r-- 1 root root  741M Oct 21 02:31 _dz32_Lucene41_0.pay
-rw-r--r-- 1 root root  791M Oct 21 02:31 _dz32_Lucene41_0.pos
-rw-r--r-- 1 root root  100M Oct 21 02:31 _dz32_Lucene41_0.tim
-rw-r--r-- 1 root root  2.7M Oct 21 02:31 _dz32_Lucene41_0.tip
-rw-r--r-- 1 root root  1.3G Oct 21 02:33 _dz32_Lucene45_0.dvd
-rw-r--r-- 1 root root  898K Oct 21 02:33 _dz32_Lucene45_0.dvm
-rw-r--r-- 1 root root   540 Oct 21 02:34 _dz32.si
-rw-r--r-- 1 root root  1.4G Oct 21 02:34 _dz32.tvd
-rw-r--r-- 1 root root  319K Oct 21 02:34 _dz32.tvx
-rw-r--r-- 1 root root   71K Jan 11 15:27 _gll0_7p.del
-rw-r--r-- 1 root root  1.1G Nov  3 10:36 _gll0.fdt
-rw-r--r-- 1 root root  398K Nov  3 10:36 _gll0.fdx
-rw-r--r-- 1 root root  1.7M Nov  3 10:40 _gll0.fnm
-rw-r--r-- 1 root root  340M Nov  3 10:37 _gll0_Lucene41_0.doc
-rw-r--r-- 1 root root  684M Nov  3 10:37 _gll0_Lucene41_0.pay
-rw-r--r-- 1 root root  769M Nov  3 10:37 _gll0_Lucene41_0.pos
-rw-r--r-- 1 root root  121M Nov  3 10:37 _gll0_Lucene41_0.tim
-rw-r--r-- 1 root root  3.2M Nov  3 10:37 _gll0_Lucene41_0.tip
-rw-r--r-- 1 root root  1.5G Nov  3 10:40 _gll0_Lucene45_0.dvd
-rw-r--r-- 1 root root  1.1M Nov  3 10:40 _gll0_Lucene45_0.dvm
-rw-r--r-- 1 root root   540 Nov  3 10:40 _gll0.si
-rw-r--r-- 1 root root  1.4G Nov  3 10:40 _gll0.tvd
-rw-r--r-- 1 root root  340K Nov  3 10:40 _gll0.tvx
-rw-r--r-- 1 root root   77K Jan 11 13:59 _itwn_7f.del
-rw-r--r-- 1 root root  1.1G Nov 13 13:57