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by ejolson
Mon Jan 18, 2016 8:35 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14625

Re: 2 node raspberry pi supercomputer

I've made the cluster, so now how do you combine the processing power to make a supercomputer? The standard API to harness the parallel processing power of a cluster for supercomputing applications is MPI. The package OpenMPI should be available in the Raspbian repositories. Except for speed, a clu...
by ejolson
Sun Jan 17, 2016 6:31 pm
Forum: Teaching and learning resources
Topic: Learning about linux(not shell)
Replies: 20
Views: 4038

Re: Learning about linux(not shell)

I thought maybe I should learn about the Linux itself, not like how to use it, but how it works, how i can alter it and etc... For example i learned about Linux kernel, drivers and sysfs from using my raspberry pi, but I want to know more, I googled and found nothing, mostly because i had no idea w...
by ejolson
Sun Jan 17, 2016 5:55 pm
Forum: General discussion
Topic: Good FTP server?
Replies: 10
Views: 50001

Re: Good FTP server?

Here are some copy tests; SSH - 3 Mbps Proftp - 6Mbps Vsftp - 7Mbps Pure-ftp - 8Mbps So yes, SSH is an option but a slow option, I would still rather go with ftp if its for internal use. The communications slowdown caused by encryption is related to the network speed versus the CPU speed. Any conne...
by ejolson
Fri Jan 15, 2016 5:29 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14625

Re: 2 node raspberry pi supercomputer

I am at a loss to understand, especially since the worst was ZERO to ZERO in "Gadget" Mode.... Zero to Zero communication must pass through the 2B. Specifically, every packet from the first Zero is sent to the 2B which then forwards it to the other Zero. Thus, it is not surprising that Zero to Zero...
by ejolson
Thu Jan 14, 2016 5:13 pm
Forum: General discussion
Topic: Ethernet/USB bottleneck
Replies: 23
Views: 7169

Re: Ethernet/USB bottleneck

Hi Guys, As per my previous post, Was wondering if anyone had tried a 5ghz 801.11ac Wi-Fi dongle, and seen if this provides more performance over USB than a LAN cable using a 100mbit connection? As WiFi is a broadcast medium where every connected device interferes with every other, putting the Pi o...
by ejolson
Thu Jan 14, 2016 6:41 am
Forum: General discussion
Topic: Ethernet/USB bottleneck
Replies: 23
Views: 7169

Re: Ethernet/USB bottleneck

NTFS needs to go. Agreed. NTFS is bad news. I would not be surprised if switching from NTFS to EXT4 gave a 50 percent improvement in file server performance. However, if you are streaming video and don't have enough bandwidth, the usual solution is to stream video at lower resolution and bit rates.
by ejolson
Thu Jan 14, 2016 6:31 am
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14625

Re: 2 node raspberry pi supercomputer

I am at a loss to understand, especially since the worst was ZERO to ZERO in "Gadget" Mode.... Zero to Zero communication must pass through the 2B. Specifically, every packet from the first Zero is sent to the 2B which then forwards it to the other Zero. Thus, it is not surprising that Zero to Zero...
by ejolson
Mon Jan 11, 2016 6:23 am
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14625

Re: 2 node raspberry pi supercomputer

fruitoftheloom wrote:110 Mbits/sec
These numbers seem much better compared to
mikerr wrote:37.6 Mbits/sec
I wonder if it is the USB cable or the Lubuntu PC instead of a Pi2B that made the difference.
by ejolson
Sun Jan 10, 2016 6:56 pm
Forum: Staffroom, classroom and projects
Topic: Setup Pi Internet through school proxy
Replies: 13
Views: 10560

Re: Setup Pi Internet through school proxy

Hello, Can anyone tell me how to configure a pi2 to use a proxy server to access the internet. As we are setting up a class of pi's we need internet connectivity on each pi, however we have to configure the browser to use a proxy. Have searched this forum and others but have yet to find clear guida...
by ejolson
Sun Jan 10, 2016 4:43 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14625

Re: 2 node raspberry pi supercomputer

While one might have hoped for a faster than 200 mbps interconnect... Hi ejolson - how do you expect to get 200 Mbps through an Ethernet interface that only has a 100 Mbps maximum theoretical instantaneous bit rate capatility? As a gigabit Ethernet dongle connected through USB obtains 220 mbps , on...
by ejolson
Sun Jan 10, 2016 8:20 am
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14625

Re: 2 node raspberry pi supercomputer

It will work fine, up to a theoretical maximum of 10Mbps. You may also have limits on the number of simultaneous TCP connections (not sure, it has been a while since I read the data sheet) I am wondering, why nobody is speaking of networking Zeros with an enc28j60 SPI2ETH chip, making use of GPIO (...
by ejolson
Sat Jan 09, 2016 10:33 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14625

Re: 2 node raspberry pi supercomputer

zero to zero: [ ID] Interval Transfer Bandwidth [ 4] 0.0-10.2 sec 52.8 MBytes 43.3 Mbits/sec Does not seem particularly speedy, but at least it works :D From my point of view creating a cluster using only a Pi B+ and three Pi zeros without any additional networking hardware is an amazing success. W...
by ejolson
Fri Jan 08, 2016 5:38 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14625

Re: 2 node raspberry pi supercomputer

mikerr wrote:Hmm - my skills are failing me with multiple pizeros :?
Any progress with zero to zero communication?
by ejolson
Wed Jan 06, 2016 7:20 pm
Forum: General discussion
Topic: Webserver
Replies: 31
Views: 4181

Re: Webserver

Round here the worst, slowest, cheapest domestic internet connections I have seen for five years or more are 10Mb/s down and 20 or more up (Yes, outgoing faster than incoming) Free with the rent or maybe 10 Euro a month. Strangely enough 20 mbps is the fastest upstream domestic connection mentioned...
by ejolson
Wed Jan 06, 2016 6:55 pm
Forum: General discussion
Topic: Webserver
Replies: 31
Views: 4181

Re: Webserver

150MB/s sounds great. I'm on their cheapest option, only 50Mb/s down. Have you tried something like http://www.speedtest.net to check that out? Yep, I've done that too. Is this upstream or downstream or both? Some services only advertise the downstream, which can be 10 to 50 times faster than upstr...
by ejolson
Wed Jan 06, 2016 12:40 am
Forum: General discussion
Topic: adding minimal GUI X windows to Jessie Lite
Replies: 2
Views: 19252

Re: adding minimal GUI X windows to Jessie Lite

I'm running fvwm on my Pi, which is light weight compared to most window managers. I think something like # apt-get install fvwm xterm xserver-org x11-apps might be enough to get started. After logging in start the window manager using xinit or startx depending on whether you want to use xauth cooki...
by ejolson
Tue Jan 05, 2016 9:22 pm
Forum: General discussion
Topic: Webserver
Replies: 31
Views: 4181

Re: Webserver

BTW, encryption can easily chew up an order of magnitude of bitrate, especially if it's being done in software, which is usually much worse. I get about 94 mbps between a Pi 2B and a Linux PC using iperf. This is pretty close to the theoretical 100 mbps hardware maximum. A Pi should be able to util...
by ejolson
Tue Jan 05, 2016 6:26 pm
Forum: General discussion
Topic: Webserver
Replies: 31
Views: 4181

Re: Webserver

The Pi 2 is roughly equal in performance to a Pentium 4 Except that many Pentium 4 motherboards have Gigabit Ethernet directly connected through CSA to the Northbridge, which is much faster than USB on the Pi. Therefore, even ignoring the advantages of SATA hard disks, Pentium 4's are much more cap...
by ejolson
Tue Jan 05, 2016 12:31 am
Forum: General discussion
Topic: Webserver
Replies: 31
Views: 4181

Re: Webserver

A question can you use raspberry pi2 in a cluster for a web server I know its possible but is it practical You can get cheap hosting for 10 dollars a month but I'd like to have physical access to my server and I want to build a quiet low energy cost web server option that I can leave running 24/7 w...
by ejolson
Mon Jan 04, 2016 11:16 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14625

Re: 2 node raspberry pi supercomputer

192.168.1.2 192.168.2.2 192.168.3.2 I think you'd find it easier to put all of the zeros in the same subnet. 192.168.1.xxx then a single iptables definition should route all three to the eth0 interface and out to the public internet. As each Pi Zero is actually connected to a different "physical" n...
by ejolson
Mon Jan 04, 2016 8:16 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14625

Re: 2 node raspberry pi supercomputer

mikerr wrote:B+ to Zero
I'm I right to interpret this as 71 mbps upstream from Zero to B+ but only 37.6 mbps downstream from the B+ to the Zero? What about Zero to Zero speeds?
by ejolson
Mon Jan 04, 2016 7:48 pm
Forum: General discussion
Topic: Pi Zero Availability
Replies: 205
Views: 48688

Re: Pi Zero Availability

You'd never know it by the feature creep people keep asking for. Granted, that has been done with the other models of Pi as well. I think the request for features in this thread, at least, is based on the idea that it will raise less eyebrows for the foundation to come out with a slightly improved ...
by ejolson
Mon Jan 04, 2016 7:24 pm
Forum: General discussion
Topic: Pi Zero Availability
Replies: 205
Views: 48688

Re: Pi Zero Availability

jamesh wrote:My preference would be a PiQuadZero, with a camera connector and Wifi, all else the same. $15? Dunno what that could be made for, but great for a lot of uses.
This would be great as long as the WiFi didn't interfere with the way the Linux Gadget driver currently works over USB on the Zero.
by ejolson
Mon Jan 04, 2016 7:17 pm
Forum: General discussion
Topic: Pi Zero Availability
Replies: 205
Views: 48688

Re: Pi Zero Availability

On the other hand, would it be possible for a third party, possibly an American NGO, to contract a large build of Pi Zeros so that the original Zero would be available in quantities large enough for use in schools?
by ejolson
Mon Jan 04, 2016 6:46 pm
Forum: General discussion
Topic: Pi Zero Availability
Replies: 205
Views: 48688

Re: Pi Zero Availability

Given their track record, we can never rule out the Foundation surprising us again with another limited edition special Pi with a different design from the Zer0, and at a different price. Even if the end result were the same, many people would feel better making a charitable contribution than being...

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