Update README.md

README.md

@@ -81,13 +81,15 @@ SeaweedFS is a simple and highly scalable distributed file system. There are two
 1. to store billions of files!
 2. to serve the files fast!
 
-SeaweedFS started as an Object Store to handle small files efficiently. Instead of managing all file metadata in a central master, the central master only manages file volumes, and it lets these volume servers manage files and their metadata. This relieves concurrency pressure from the central master and spreads file metadata into volume servers, allowing faster file access (just one disk read operation).
+SeaweedFS started as an Object Store to handle small files efficiently. Instead of managing all file metadata in a central master, the central master only manages file volumes, and it lets these volume servers manage files and their metadata. This relieves concurrency pressure from the central master and spreads file metadata into volume servers, allowing faster file access (O(1), usually just one disk read operation).
+
+SeaweedFS can be tiered to the cloud. With hot data on local cluster, and warm data on the cloud with O(1) access time, SeaweedFS can transparently achieve both fast local access time and elastic cloud storage capacity.
 
 There is only 40 bytes of disk storage overhead for each file's metadata. It is so simple with O(1) disk reads that you are welcome to challenge the performance with your actual use cases.
 
 SeaweedFS started by implementing [Facebook's Haystack design paper](http://www.usenix.org/event/osdi10/tech/full_papers/Beaver.pdf). Also, SeaweedFS implements erasure coding with ideas from [f4: Facebook’s Warm BLOB Storage System](https://www.usenix.org/system/files/conference/osdi14/osdi14-paper-muralidhar.pdf)
 
-SeaweedFS can work very well with just the object store. [[Filer]] can then be added later to support directories and POSIX attributes. Filer is a separate linearly-scalable stateless server with customizable metadata stores, e.g., MySql/Postgres/Redis/Etcd/Cassandra/LevelDB/MemSql/TiDB/CockroachDB.
+On top of the object store, optional [Filer] can support directories and POSIX attributes. Filer is a separate linearly-scalable stateless server with customizable metadata stores, e.g., MySql/Postgres/Redis/Etcd/Cassandra/LevelDB/MemSql/TiDB/CockroachDB/etc.
 
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