IBM 2305

The IBM 2305 Direct Access Storage Facility was a fixed-head disk drive originally announced in 1970 to connect to the 360/85 and 360/195 using the IBM 2880 Block Multiplexor Channel. The 2305-1 ran at 3.0 MB/second when attached using the 2-byte channel interface, and the larger 2305-2 ran at 1.5 MB/second.
The 2305/2835 Storage Facility became popular with the System/370, and used as the paging device of choice, for systems 155-2, 158, 165-2 and 168. This was particularly true at IBM internal data centers where obsolete equipment was often all that was available. When floor space was not at a premium, the fixed head storage devices gave paging performance comparable to the alternative of using only the small amount of disk space located under one seek position of a standard disk drive and leaving the rest of the volume empty, which was a common practice in high transaction environments such as airline reservation systems, for paging and high volatility data storage.