<title>Use Of A Digital Optical Storage System</title>

Abstract

AbstractThe Common File System (CFS) is a file management and file storage system for the Los Alamos National Laboratory's computer network. The CFS is organized as a hierarchical storage system: active files are stored on fast-access storage devices, larger, less active files are stored on slower, less expensive devices, and archival files are stored offline. Files are automatically moved between the various classes of storage by a file migration program that analyzes file activity, file size, and storage device capabilities. This has resulted in a cost-effective system that provides both fast access and large data storage capability (over 9 trillion bits currently stored). A large capacity (IQl^ bits), reliable Digital Optical Storage System would replace the offline storage as the archival part of the CFS and might also be used for active storage if it had a reasonable file access time.IntroductionThe Common File System (CFS) is a centralized file storage system for a local network of 40 computers that run 5 different operating systems. CFS was developed to provide a large data storage system available to all computers in the Network, to allow convenient and controlled sharing of files between computers and users, and to provide a master directory for good management and control of data. Access to all CFS storage devices is only through the CFS control processors using a small precisely defined set of functions. Users store and retrieve information as named files and need have no knowledge of CFS storage devices because the CFS determines where the files reside. CFS has been operational since June 1979 and is used 24 hours a day, 7 days a week.The Network environmentA functional view of the Los Alamos computer network is shown in Figure 1. The Network has a core of worker machines that currently includes five Cray-lS supercomputers and four CDC 7600s with a combined capability of over 240 million floating-point operations per second. Smaller machines, such as the DEC VAX 11-780 and the CDC Cyber 170/825 are used as special-purpose worker computers. All the worker machines run timesharing operating sys­ tems. They are front-ended by a communications network of over 2500 terminals that service 3500 users and are back-ended by a file transport network that includes the CFS file storage system, the Print and Graphics Express Station (PAGES) output system, and the Extended Net­ work Access System (XNET) that connects many distributed processors to the Network. The file network also provides for worker machine-to-worker machine file and message shipping.Common File SystemThe CFS configuration is shown in Figure 2. Two IBM 4341 computers serve as primary and backup control processors. All CFS production programs run in the primary control pro­ cessor. If the primary processor fails, the production programs can be switched to the backup in a matter of minutes.The CFS programs run as application programs with no modifications to the IBM operating system. Most of these program modules are written in PL/1, with Assembler being used for only a few modules. The CFS software has been exported to other installations with similar mass storage devices. fThe CFS uses three online storage systems: an IBM 3350 disk system, an IBM 3380 disk system, and an IBM 3850 Mass Storage System with an online capacity of about 2.7 trillion bits. An archival storage capability is provided by ejecting cartridges containing inactive files from the 3850 and storing them in cabinets. The disk, the 3850, and offline storage are organized as a storage hierarchy. Active files are stored on disk, less active and larger files are stored in the 3850, and inactive files are stored offline on archival car­ tridges .In mid-January 1983, users had stored 770,000 files, which occupy 9 trillion bits of storage. The growth is currently 290,000 files and 4 trillion bits per year. The typical daily activity is 12,000 file accesses with 60 billion bits of data transferred. The peak period usage averages 1200 file accesses with 5 billion bits of data transferred per hour.55