Jim Rambo (rambo@sulcus.med.yale.edu)
Thu, 22 Jul 1999 14:07:29 -0400
Recently, I looked at solving your problem the same way that Sean proposed.
We wanted to perform interactive, real-time volume visualization, rendered
on
an Onyx2 while remotely displaying and interacting with the visualization on
an
O2 (remote host) using glReadPixels and glDrawPixels and passing the
rendered
2D image across a dedicated fiber channel network. Although we didn't
actually
purchase the system that is discussed below, we did configure it on paper
and
found that the solution depends on a number of factors, including the
following:
1) overall desired display rate
2) potential bottlenecks (i.e. render, transmission, and display rates) for
your image and data
3) number of graphics pipes used for rendering and number of nodes you wish
to
display to
4) budget
5) amount of time available for coding your IPC (sockets) software
6) whether you'll be compressing/decompressing your rendered images
before/after you transmit them to the remote host
7) amount of time available for recoding IPC software updates.
We found that Prisa Networks offers a reasonably priced system (hardware and
software) that can, in theory, meet our requirements mentioned above for
around
$12K.
The solution we looked at combines a fiber channel network with IPC software
called, "Transporter". Transporter is a protocol with proprietary API for
talking between hosts using sockets. According to Prisa, if you use sockets
and a fiber channel network without Transporter, your network bandwidth
maxes
out at about 20 MB/s. However, with Transporter, network throughput
increases
to 80-90 MB/s. The cost for a managed-loop hub that provides a single
point-to-point connection is as follows:
1) $8K for 4 fiber channel cards (1 card for each node and 2 cards on the
hub
for both nodes; cards cost $2K each)
2) $1.5K for a managed loop fiber channel hub (provides up to 8 ports;
however,
the bandwidth for multiple pt-to-pt connections is shared among all
connections)
3) $2K for 2 licenses of Transporter (1 for the rendering host and 1 for the
display host; licenses cost $1K each)
Thus, total cost for this configuration is around $12K. Of course, you could
write your own IPC software. However, it takes time to write and update.
Also, if you wish to provide multiple connections between renderers and
displays, that also takes time (Prisa also offers a fiber channel switch
that
provides multiple pt-to-pt connections that pass data simultaneously at
80-90
MB/s). Furthermore, you can use cheaper or more expensive network
configurations. Again, cost, time, and desired display rate all factors to
consider.
Hope this helps - regards,
Jim
-- James V. Rambo Yale University Graphics Specialist School of Medicine Voice: 203-785-4905 Diagnostic Radiology Fax: 203-737-4273 333 Cedar St, BML 332 james.rambo@yale.edu New Haven, CT 06520-8042
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