This robotic arm holds one of the 6,000 tape cartridges in a StorageTek 9310 tape library. Each tape cartridge holds 20 to 200 gigabytes of data.

SCD operates five of these automated libraries in the NCAR supercomputing center. The StorageTek 9310s hold data that is being used regularly. Archival data is stored in cartridges on shelves that are mounted and unmounted by the computer operations staff.

Photos courtesy StorageTek

NCAR's MSS surpasses 2 petabytes of data stored

On 21 July 2004, NCAR's Mass Storage System (MSS) surpassed 2 petabytes of data storage, including second copies. NCAR's MSS is a central, large-scale data archive that stores data used and generated by climate models and other programs executed on NCAR's computers. Built by SCD staff over a period of 18 years, this one-of-a-kind data facility is often called one of NCAR's "crown jewels."

In November 2002, the MSS reached 1 petabyte of data stored, and now its holdings have doubled only 20 months later. This growth is made possible by the StorageTek automated tape libraries shown here. Human operators cannot match the speed or quantity of mounts and dismounts needed to support the more than 1,200 researchers who access the existing data and add another 60 terabytes of new data each month. The five StorageTek 9310 tape libraries perform up to 1,750 mounts and dismounts every hour, day and night. This level of usage places high demands on the tape-handling system.

Of the 2 petabytes of data in the MSS, 1.04 petabytes of the most frequently used data are handled by the automated tape libraries. All of the primary copies of the data are held in the automated libraries, and second copies are held on shelves managed by computer room staff.

In the late 1970s, the data storage facility at NCAR was regarded as a very high capacity data archive. Back then, it held .002 to .003 petabyte (2 to 3 terabytes) of data. About 25 years later, its holdings reached 1 petabyte. Now less than two years after that, the MSS holds 2 petabytes and is increasing by .06 petabyte each month. The demands on this system are growing so rapidly because of the great increase in the output of modern supercomputers.

This ever-increasing demand for more data to be stored and retrieved more rapidly requires SCD's MSS Group to develop and implement creative and robust solutions to the problems that arise. They are currently working to upgrade the MSS communication network for higher bandwidth. This will allow them to use new tapes in the automated tape libraries that can hold more data and transfer it faster. The result of their current work will be to triple the data capacity and also triple the data transfer speed in the automated tape libraries.

The 1-petabyte milestone for the MSS is described at NCAR's MSS exceeds 1 petabyte.

— Brian Bevirt