nessDB1.7有了很大的改进，详情见：
http://www.cnblogs.com/overred/archive/2011/10/24/nessDB1_7.html
nessDB v1.5已经启用B+ Tree作为索引结构。
Bencnmark results:
Benchmark(100,0000 entries, 10000 queries)
=========================================================
Keys: 20 bytes each
Values: 100 bytes each
Entries: 10000000
IndexSize: 648.5 MB (estimated)
DataSize: 1030.0 MB (estimated)
--------------------------------------------------------------------------------------------------------------
nessDB: version 1.5(B+ Tree)
LRU: closed....
Date: Sat Aug 27 14:47:04 2011
CPU: 2 * Intel(R) Pentium(R) Dual CPU T3200 @ 2.00GHz
CPUCache: 1024 KB
+-----------------------+---------------------------+----------------------------------+---------------------+
|write (succ:10000000): 0.000016 sec/op; 63728.0 writes/sec(estimated); 10.7 MB/sec; cost:156.917(sec)
+-----------------------+---------------------------+----------------------------------+---------------------+
|readseq (found:10000): 0.000007 sec/op; 133891.6 reads /sec(estimated); 22.5 MB/sec; cost:0.075(sec)
+-----------------------+---------------------------+----------------------------------+---------------------+
|readrandom (found:10000): 0.006636 sec/op; 150.7 reads /sec(estimated); 0.0 MB/sec; cost:66.361(sec)
+-----------------------+---------------------------+----------------------------------+---------------------+
Completely Cold-Start(echo 3 > /proc/sys/vm/drop_caches):
+-----------------------+---------------------------+----------------------------------+---------------------+
|readseq (found:10000): 0.000022 sec/op; 44915.5 reads /sec(estimated); 7.5 MB/sec; cost:0.223(sec)
+-----------------------+---------------------------+----------------------------------+---------------------+
|readrandom (found:10000): 0.012902 sec/op; 77.5 reads /sec(estimated); 0.0 MB/sec; cost:129.019(sec)
+-----------------------+---------------------------+----------------------------------+---------------------+
|removerandom (found:10000): 0.006539 sec/op; 152.9 reads /sec(estimated); 0.0 MB/sec