[Udpcast] Speed dropping down

Michael D. Setzer II mikes at kuentos.guam.net
Fri Mar 25 22:17:16 CET 2005

Not sure if this applies to your situation, but this is what I  
have done in recent work to add udpcast as an option with  

I use G4L to create a image file on my server using lzop  

I can then use  
udp-sender --file image --max-bitrate 80m 

What I originally tried on the clients didn't work, and I got a  
reply that worked perfectly. 

Why don't you simply use  
udp-receiver --pipe 'lzop -d -c -' -f /dev/hda ? 

I've also used the latest options to build boot diskettes that I created  
with the mac table to assign ip addresses to each machine, and just  
ran the model machine with sender mode with only the --max-bitrate  
80m option to 19 machines. Setup the diskettes with default lzop  
compression. Took about 50 minutes to image to 19 machines with  
80 gb drives.  

One last issue that I found in making images, is that clearing out  
unused sectors makes a big difference. I did an image of a clean  
install of linux on a drive, and it created a 12GB file. I then blanked  
out the unused sectors, and got a 2.5GB file. 
dd if=/dev/zero of=/0bits 
rm /0bits 

I've never used the PXE, so don't know if this doesn't apply, but it is  
things that I found that make the udpcast work great for me. 

Again, a geat program.  
On 25 Mar 2005 at 18:02, Lukas Kolbe wrote: 

From:           	Lukas Kolbe <lucky at knup.de> 
To:             	udpcast at udpcast.linux.lu 
Date sent:      	Fri, 25 Mar 2005 18:02:11 +0100 
Subject:        	[Udpcast] Speed dropping down 

> Hello! 
> First of all, thanks for this extremely useful tool. 
> We use it to copy hd-images to a pool of 48 PCs, and it works 
> surprisingly well. At least, last semester it did :).  
> We use PXE to boot all clients into a small debian-system with r/o 
> nfs-roots, and cluster-ssh to control them all at once (eg., start 
> udp-receiver). Network is 100mbit half-duplex, the switch can 
> 102gbit internally. Unfortunately, we have no physical access to 
> switch. 
> On the server, we use this command to cast the complete 
> cat /dev/hda | lzop -c - | udp-sender --half-duplex --max-bitrate 
> On the clients, the opposite is: 
> udp-receiver | lzop -d - | dd of=/dev/hda 
> hda has about 29gb of used data, and a capacity of 80Gb. We do 
about 16 
> clients at the same time, and the first round went very well (it took 
> about 105 minutes to write the whole disk). 
> Now, the problem for the second 16 (which are the same 
hardware than the 
> first 16) is, that the speed of udpcast has dropped down from 
> 50mbit/s (with which it transferred about 24Gb) to right now about 
> 50kbit/s (with which it has transferred about 5gb yet) (that's ok for 
> now, as they can finish writing the image over the easter-
weekend), with 
> many timeoutnotanswered-messages on the sender. 
> These messages came from all clients every few seconds when 
the speed 
> was about 50mbit/s, but the client number 2 was overrepresented 
> and the speed dropped down to about 50kbit/s, so I cut it off.  
> When udpcast reduces the speed to that of the slowest receiver, 
and that 
> receiver gets cut off, would it be possible that the speed gets up 
> again? At the moment it doesn't seem so ... 
> Thanks in advance, Lukas 
> _______________________________________________ 
> Udpcast mailing list 
> Udpcast at udpcast.linux.lu 
> https://lll.lgl.lu/mailman/listinfo/udpcast 

  Michael D. Setzer II -  Computer Science Instructor      
  Guam Community College  Computer Center                  
  mailto:mikes at kuentos.guam.net                            
  mailto:msetzerii at gmail.com
  Guam - Where America's Day Begins                        

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