[Udpcast] tg3 ethernet

Alain Knaff alain at knaff.lu
Tue Jan 30 10:00:35 CET 2007

Adrian Stewart wrote:
> Using UPDCast (CD Version) in a lab of 48 IBMs with SATA drives and
> broadcom (5787) gigabit NICs.  I'm not sure why, but when I start a
> group of machines the transfer process goes along at a slow pace of
> 54Mb. 
> The network is all Linksys 1GB switches. Why is the xfer rate so low?
> I've used UDPcast with the tg3 driver in the same setup with xfer rate
> upwards of 500Mb. This machine has USB only (keyboard and mouse). I
> finally got the keybaord to work but the xfer
> I've downloaded Cast-0-matic hoping that would resolve the xfer rate
> issue but to no avail. Please advise. I'm new to Linux/Unix and dont
> know how to compile an image with the new driver from Broadcom.com.
> Thanks

You say that formerly you got it to work (with the same network cards 
presumably) at 500 Mbit/s . So what exactly changed between both 
situations (apart from keyboard and mouse, which I don't think are the 

Some possible ideas:
- Switches? (Some switches do have trouble with multicast)
- Hard disks? (Not all disks may be capable of 500 Mbit/s)
- Content? (Especially if you operate in compressed mode. Compression 
helps you when the network is the bottleneck, but doesn't speed up disk 
access. So if you have very compressible data, such as lots of zeroes, 
you'll see a very low network transfer rate, because less data needs to 
be transmitted, but it still needs to be read from disk)
- BIOS Sata configuration? (with "Legacy" setting, some machines access 
their disks *much* more slowly)
- Udpcast version (if that changed, when was the last one that worked? 
Do you still have it around to test that one again)
- ...



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