What's a KFQSA?

From: Seth J. Morabito <sethm_at_loomcom.com>
Date: Wed Apr 22 01:51:14 1998

> By the way, What's DSSI?

Well, it appears to be Yet Another variation on SCSI, but with more
Oomf. (how's that for a really clever way of admitting "I don't know
the protocol details"? :)

Seriously though, it's both a disk bus and a host interconnect for
VAXen. I don't know if PDP's ever used DSSI, though I imagine they
probably did.

Each DSSI disk (RFXX series DEC disks) has a complete "host" built
into the on-disk logic board. The disk firmware acts like a little
tiny host, for sharing in a cluster for instance, or for just
talking to the KFQSA controller. This allows each RFXX disk to do
low-level sharing in a cluster, handling requests for disk access
from remote hosts without relying on the VAX host to take care of
processing them, apart from handling the Ethernet<->DSSI bridge if
Ethernet is being used as the cluster interconnect.

You can also connect two VAX computers directly together over a
DSSI bus, using an external DSSI cable.

On a VAX, you can do this at the console ROM monitor:


Upon hitting <enter>, you are connected to the on-disk firmware
of DISK 0, where you can perform diagnostics, change firmware
settings, format the disk, run tests, and so forth. Really quite
neat. I'm sure other disk connections do this, but DSSI is the
only one I'm familiar with.

Anything else out there like this?

Received on Wed Apr 22 1998 - 01:51:14 BST

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