I heard it is possible to "telnet to the hard disk" on VAX systems where the HD is connected with a DSSI interface. What commands are available once one establishes a connection to the disk?
The RF Series Integrated Storage Element User Guide is available as PDF e.g. here.
On page 3-10 (p.88 in the PDF), it lists the commands to "telnet" (not really) to the ISE (here, to run the
$ MCR SYSGEN
SYSGEN> CONNECT/NOADAPTER FYA0
$ SET HOST/DUP/SERVER=MSCP$DUP/TASK=PARAMS <node_name>
On page 2-32 (p.72 in the PDF), there's a table of available programs:
PARAMS: A SYSGEN-like parameter editor and interactive query utility used to view ISE and DSSI bus status.
HISTRY: An abbreviated version of a portion of PARAMS. HISTRY is used by host-level software such as MDM.
DIRECT: A directory program, output only, that lists the available diagnostic and utility programs.
PRFMON: An abbreviated version of a portion of PARAMS. PRFMON can be used by host-level software such as the VAX performance analyzer (VPA).
DRVEXR: A comprehensive drive exerciser.
DRVTST: A quick pass/fail test of the drive.
VERIFY: A complete read check of the disk and verification of the DSDF1 on- disk structure.
ERASE: A data ``scrubber'' utility that writes alternating patterns to each LBN, including the second sector of the RCT and the previous locations of the bad blocks, and then verifies that the scrubbing process succeeded.
DKUTIL: An interactive block display and replace utility. Typically used to confirm ERASE scrubbing.
Page 2-18 (p.58 in the PDF) contains an example list of running threads (processes) in the ISE. The CPU apparently was an 680x0.