File migration in the NCAR mass storage system

Abstract

As of July 25, 1988, the mass storage system (MSS) at the National Center for Atmospheric Research (NCAR) contained 55.8 tb of user data in more than 291000 bitfiles averaging greater than 23 megabytes (MB) in size. The bulk of the data is housed in a (nonautomated) library of IBM 3480 tape cartridges, and the remainder resides temporarily on a disk farm of IBM 3380e disks. A discussion is presented of the strategy used in developing an effective management policy for the movement of files between the disk farm and tape library, the algorithms chosen, the mechanisms implemented for tuning those algorithms, and the effects on system performance experienced as a result. >