[Beowulf] Re: newbie's dilemma / firewire? (Hahn)

[Ed Karns]

On Mar 7, 2006, at 3:57 PM, Mark Hahn wrote:

>> effective in some cases. However, the bulk file transfer rates for  
>> very large files via FireWire 400 (1394a) is significantly faster  
>> than 1000baseT and FireWire 800 (1394b) is more than 240% faster  
>> that  GigaBit EtherNet.
>
> can you show some references for this?  it's hard to understand why  
> a 400 Mbps connection would be "sigificantly faster" than a 1000 Mbps
> connection.  or are you talking mainly about shortcomings in some  
> platform's drivers/stack?
>

Easiest, simplest reference is this image: http://unibrain.com/ 
products/assets/FireNET5.jpg  ... or read the whole report at bottom  
of: http://unibrain.com/products/driverapi/firenet.htm

Note that for large files, the FireWire network bulk file transfer  
rates can exceed GigaBit performance. The above reports (arguably  
promotional) are for FireWire 1394a (400 Mbits / second). When  
similar tests are run on FireWire 1394b (800 Mbits / second),  
performance can exceed 240% of network bulk file transfer (write  
times) of GigaBit EtherNet.

Why is it comparable to or faster from a processor running at around  
40% of GigaBit processor speeds? Processor efficiency FireWire has a  
32-bit "risc" type microprocessor, is peer to peer in hardware /  
firmware and has other lean architecture features. (Small address  
space, data frame large = more efficient data packet over double  
duplex connections.)

A down side?: FireWire 1394a (now called FireWire 400) has an address  
space of maximum 64 nodes, maximum and optimally less than 32 nodes  
(less than 16 recommended). FireWire 1394b (now called FireWire 800)  
can address a maximum of 128 nodes, but because of the nature of the  
topography ("quad duplex" or double, double duplex, twice as many  
connections at same processor speed), optimum performance is still  
achieved from less than 32 nodes.

Future: there are prototypes of FireWire 1600 and 3200 operating over  
fiber and using multiple "colors" ... using two fibers (duplex),  
multiplexed by frequency discrimination (4 or 8 channels) using the  
same FireWire 800 (Texas Instruments chips) ... comparable to ~~  
64000baseT ... and the involved engineers say they can stay ahead of  
Moore's Law beyond several more years.

Ed Karns
FireWireStuff.com