Hierarchical Storage Controller
The Hierarchical Storage Controllers (HSC) were a series of stand-alone, intelligent mass storage controllers, created by DEC for use in VAXcluster system. They were connected to the VAX systems in the VAXcluster over Computer Interconnect links.
An HSC supports a number of disk and magnetic tape 'data channels' - the exact number of each depends on the HSC model. Disk data channels use the Standard Disk Interconnect (SDI), and can support up to four drives on each. Tape data channels use the Standard Tape Interconnect (STI), and can support up to four formatters on each; the number of magnetic tape drives per formatter will depend on the formatter. (Dual-ported drives are supported, so that each drive is accessible via two HSC's, further improving reliability.)
Physically, an HSC consists of a number of boards mounted in a card cage held in an H9642 cabinet, along with power supply units. The drives are mounted in additional cabinets. Logically, an HSC contains:
- a CI interface
- port processor
- port buffer
- port link
- a control processor
- cache memory (optional on HSC90 and later models)
- disk data channel(s)
- tape data channel(s)
- SCSI data channel (optional on HSC70 and later models)
Several different HSC models were produced:
The HSCs needed a special software (kind of an operating system) to run, the official software name was HSC (same as the hardware), the project name, CHRONIC, was sometimes used instead.
The time to boot an HSC varied with the boot device; the TU58 took more than 6 minutes, the RX33 less than one and a half minute.
- HSC User Guide (AA-GMEAA-TK) - not online
- HSC - documentation at Bitsavers
- HSC Controller Installation Manual (EK-HSCMN-IN-002)
- The Hierarchical Storage Controller, A Tightly Coupled Multiprocessor as Storage Server - in Digital Technical Journal, Volume 1, Number 8 (February 1989); on pp. 10-26 of the PDF