data storage location

Gerry Creager N5JXS gerry.creager at
Thu Sep 11 09:39:45 EDT 2003

We have seen less than stellar performance with the older/cheaper ATI 
Centrecom switches.  We were almost completely unsuccessful with 
multicast tests.  And RFC2544 packet testing was the pits.  So: small 
packets are bad, and multicast appears problemmatic.  At least on these 


Felix Rauch wrote:
> On Wed, 10 Sep 2003, Guy Coates wrote:
> [...]
>>Recently we've had some success using multicast methods to distribute data
>>to large numbers of nodes. udpcast is one of
>>the better multicast codes, but you'll need to put some wrappers around it
>>to make it useful. The multicast method is substantially faster than
>>rsyncing data on large clusters.
> I had two problems when testing UDPcast:
> - A cheaper ATI CentreCom Fast-Ethernet switch multicasted data only
>   with the speed of the slowest connected machine, even if that
>   machine was *not* part of the multicast group. I had to unplug all
>   10 Mbps links to speed up UDPcast above 1 MByte/s.
> - With Gigabit Ethernet and a smaller cluster of 1 GHz PentiumIII
>   machines I had to set a rate limitation on the sender. Otherwise the
>   sender and the receivers lost synchronization and the transmission
>   didn't work.
> However, if you forgive me a short bit of advertising, we use the
> "Dolly" programm to replicate large amounts of data in our clusters:
> It replicates data with a multi-drop chain over TCP and scales quite
> nicely. We only had performance problems on a switch with a rather
> limited backplane, but otherwise we use it regularly in our 16- and
> 128-node clusters.
> - Felix

Gerry Creager -- gerry.creager at
Network Engineering -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.847.8578
Page: 979.228.0173
Office: 903A Eller Bldg, TAMU, College Station, TX 77843

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