unique worldwide tape names

rdv at ISI.EDU rdv at ISI.EDU
Mon Aug 12 10:27:28 PDT 1996


* From the SCSI Reflector, posted by:
* rdv at ISI.EDU
*
(Netstation is a new system architecture built around network-attached
peripherals; see http://www.isi.edu/netstation/) 

Bob Baird suggests IP addresses as worldwide names for storage devices.

This is exactly what we have done in the Netstation project here at
ISI.  Well, almost; we are in fact using domain names rather than IP
addresses for most purposes.  A drawback to this approach is that
domain names are variable-length; an advantage is that they are
human-readable, and the mapping to address can be varied when needed
(e.g. when subnets change).

Even mentioning using IP addresses for devices opens the question of
What network/transport protocols are appropriate for devices; so far,
Fibre Channel and SSA and whatnot have done their own, rather than
relying on the existing body of network research.  Even within
the Netstation project, where most of the members come from the
networking community, at first we felt a device-specific transport was 
necessary to get the performance we wanted, but we have now decided
that TCP will be adequate, and are shifting to using that.

Keep in mind that IPv6 addresses are 128 bits.  SCSI-3 defines device
identifiers as 64 bits architecturally, with the number actually in
use being interconnect-dependent.

Several options for demultiplexing are available; first, by protocol
(TCP, UDP), then port number, then sometimes within the port, such as
program number and RPC number at the RPC port.

The node manager itself must be available at a well-known port to
identify the types of devices and services, as well as current
ownership/availability (reservation) state.

We have recognized that we need to support multiple devices at a
single network address, but haven't done a whole lot about it.  They
will probably be supported at different ports, as Bob has outlined.

A key feature is that devices should be able to support multiple
interfaces; a SCSI interface, an IPI interface, an NFS interface, a
BDS interface, a derived virtual device (DVD) interface are all
possible.  These are all available either at separate ports at the
network address, or as separate programs at the RPC port.  For our DVD 
model, access is requested from the node manager and bound to a port
dynamically.

Many of you will be at the Goddard conference next month, keep an eye
out for our paper on derived virtual devices if you're interested.

		--Rod

****************************************************************************
Rod Van Meter USC/ISI rdv at isi.edu,rdv at alumni.caltech.edu +1(310)822-1511x417
****************************************************************************
The Unity of Freedom has never relied on uniformity of opinion.
                                                              -- JFK





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