System and method for data placement in multiple tier storage systems

In a storage system including a first tier and a second tier a method includes: storing access statistics per object; obtaining a request to perform a write operation; calculating a recency factor to the first object based on the access statistics; and writing the first object to one of the first tier and the second tier, depending on the recency factor. Performing garbage collection process on the second tier may include: reading metadata of an object stored in the second tier; determining whether the object is valid based on the metadata; if the object is invalid, discarding the object; and if the second object is valid: calculating a recency factor for the object based on the access statistics of the object; and moving the object to the first tier or leaving the object in the second tier, depending on the recency factor of the second object.