MSS Introduction
Hierarchical Storage Management Systems
The Mass Store System (MSS) is a system designed to conveniently store many millions of files constituting of hundreds of terabytes of data. Because it is certainly not cost-effective to store this amount of data on disk, tape is also utilized for data storage. This disparity in media is handled by what is known as a Hierarchical Storage Management (HSM) system.
An HSM is designed to transparently maintain data across a variety of heterogeneous storage devices that are organized into a hierarchy: fast, expensive, low-volume devices (e.g., disks) normally occupy the higher levels of the hierarchy, while slow, inexpensive, high-volume devices (e.g., tape drives) occupy the lower levels. Data typically enter the system through the higher levels; as data age, they are migrated to lower levels. On retrieval, data are automatically and transparently staged back to higher levels for access. Because the higher levels are of limited size, aged data, once migrated, are purged or truncated from the disk.
Because of the transparent nature of referring to data on an HSM, makers of HSMs like to promote the concept that they may be viewed as "one big, virtual disk". This analogy goes only so far, as it neglects the time needed to stage data from lower levels in the hierarchy to higher levels. However, from a usage standpoint, the data may be accessed such as if they indeed are on disk.
StorNext
StorNext is the HSM that runs on the newest MSS. It is the next generation of FileServ/VolServ (below).
FileServ/VolServ
FileServ is the name of the software that implements the HSM on the new MSS. Its sister product, VolServ handles the tape robotics system. FileServ/VolServ is similar in many ways to UniTree, the HSM software that drove the original MSS. (For a review of the original MSS, and for more information on HSMs, please see the Data Storage and Retrieval System (DSRS) documentation.)
