创建快照时会创建manifest.json，此文件的用途是什么？我原以为它包含了快照中所有文件的列表，它们是：
2014-11-11 17:36:51 43 keyspace-cf-ka-1-CompressionInfo.db
2014-11-11 17:36:51 87 keyspace-cf-ka-1-Data.db
2014-11-11 17:36:51 10 keyspace-cf-ka-1-Digest.sha1
2014-11-11 17:36:51 16 keyspace-cf-ka-1-Filter.db
2014-11-11 17:36:51 25 keyspace-cf-ka-1-Index.db
2014-11-11 17:36:51 4460 keyspace-cf-ka-1-Statistics.db
2014-11-11 17:36:51 101 keyspace-cf-ka-1-Summary.db
2014-11-11 17:36:51 91 keyspace-cf-ka-1-TOC.txt
2014-11-11 17:36:51 43 keyspace-cf.field2_field1_idx-ka-1-CompressionInfo.db
2014-11-11 17:36:51 63 keyspace-cf.field2_field1_idx-ka-1-Data.db
2014-11-11 17:36:51 9 keyspace-cf.field2_field1_idx-ka-1-Digest.sha1
2014-11-11 17:36:51 16 keyspace-cf.field2_field1_idx-ka-1-Filter.db
2014-11-11 17:36:51 25 keyspace-cf.field2_field1_idx-ka-1-Index.db
2014-11-11 17:36:51 4458 keyspace-cf.field2_field1_idx-ka-1-Statistics.db
2014-11-11 17:36:51 101 keyspace-cf.field2_field1_idx-ka-1-Summary.db
2014-11-11 17:36:51 91 keyspace-cf.field2_field1_idx-ka-1-TOC.txt
2014-11-11 17:36:51 62 manifest.json
但它包含：
{
"files": [
"keyspace-cf.field2_field1_idx-ka-1-Data.db"
]
}