IEEE 1394

Donald Becker becker at
Thu Dec 5 06:02:51 PST 2002

On Thu, 5 Dec 2002, Eugen Leitl wrote:

> After I've posted a link to the Oracle library for clustering over 1394 
> a while back Apple mumbled something about RFC 2734 (IP over 1394):
>  All Apple computers sold today include one or more FireWire ports. 
>  Because FireWire can transfer data at up to 400 megabits/second, it is 
>  suitable for networking and clustering solutions, as well as temporary 
>  connections to the internet using Internet Sharing.

By "clustering" they mean fail-over.
  "N-way clustering, where N<=2".

If you want scalable performance and matrix availability, you will need
an IEEE1394 switch.  Pretty much every vendor with an 10Gb Ethernet
switch also makes IEEE1394 switches ;->  (N=0)

> Since I've never seen real numbers for IEEE 1394 latency I did some 
> websearches, and finally found some meat:

We never see them because (!!!)

> "The IEEE 1394 bus has a minimum latency of a few hundred microseconds and 
> a worst-case delay of a few milliseconds.

I think that they are very optimistic with that worst-case delay.

> For large data blocks, this bus 
> uses direct memory access (DMA) similar to PCI bus mastering that reduces 
> the influence of software protocol overhead on the transfer rate.

This is great for fixed-sized repeated frames such as video or
contiguous disk block reads, but adds additional overhead for other
communication.  And most cluster communication is "other".

Donald Becker				becker at
Scyld Computing Corporation
410 Severn Ave. Suite 210		Scyld Beowulf cluster system
Annapolis MD 21403			410-990-9993

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