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
• memory
• 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:

• HSC40
• HSC50 (1983)
• HSC60
• HSC65
• HSC70 (1985)
• HSC90
• HSC95

A number of adapters are available, to connect SCSI devices to the various buses used by HSC systems:

• HSD10 DSSI-to-SCSI Bus Adapter
• HSG60 FC-to-SCSI Bus Adapter
• HSJ30 CI-to-SCSI Bus Adapter

HSC Software

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, CRONIC (Colorado Rudimentary Operating Nucleus for Intelligent Controllers), was sometimes used instead.

The HSC software was distributed on TU58 tape cartridges for the HSC50 and on RX33 floppy disks for all other HSC models.

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.

See also

• DEC CI Hierarchical Storage Controllers

Further reading

• HSC User Guide (AA-GMEAA-TK) - not online

External links

• HSC - documentation at Bitsavers
• HSC Controller Installation Manual (EK-HSCMN-IN-002)
• VAXcluster Maintenance Student Workbook: Volume 2 (EY-9222E-SB-0001) - this volume is dedicated to the HSC
• 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