Updated Amazon S3 API (markdown)

Amazon-S3-API.md

@@ -8,6 +8,8 @@ Each bucket is stored in one collection, and mapped to folder /buckets/<bucket_n
 
 A bucket can be deleted efficiently by deleting the whole collection.
 
+From version 3.51 name of collection is `filerGroup_bucketname` or `bucketname` if filer group is not set.  
+
 ## Support Many Buckets
 
 Each bucket has its own collection. Usually one collection uses 7 volumes, where each volume is 30GB by default. So if you want to create multiple buckets, you may run out of volumes very quickly unless you have a large disk.