mrgreaper
Posts: 42
Joined: Sat Aug 31, 2013 10:49 pm

thinking of buying a pi need some advice

Sat Aug 31, 2013 11:23 pm

Im looking at the pi on amazon ( http://www.amazon.co.uk/Raspberry-Pi-Mo ... B009SMWSQA ) money is very tight at mo but this does seem fairly cheap.

i want to set it up as a usenet downloader (thinking sabnzbd, seen a few guides about that so i know finding out how to will be easy)
i also want it to act as a rtmp server (i currently use http://obsproject.com/forum/viewtopic.php?f=18&t=5873 so i should be able to adapt that) this would also mean i would have my own website ...not sure what i would use that for but hey im sure i`ll find something for it lol.
and finaly as a media server, so any films or tvshows that may be on the attached hard drive can be viewed on my ps3 or accessed via my pc/laptop. (i use ps3 media server for this..but no idea how to do that on linux but im sure theres guides all over the place for that)

So heres my questions:
1) will i be asking too much from it?
2) i have heard there is an issue with pi`s and download speeds, ( i have a 120meg download 6 meg upload, its the fastest in my city, but i know some countrys are much faster) so given my speed will i have a bottle neck with the downloads (the hard drive ill use to recieve the downloads whill either be a network drive or plugged directly into the usb, which either is advised)
3) If i buy the device i linked to will i have all i need? (i have a usb kb/mouse and hdmi tv)

thanks in advance

itimpi
Posts: 1088
Joined: Sun Sep 25, 2011 11:44 am
Location: Potters Bar, United Kingdom
Contact: Website

Re: thinking of buying a pi need some advice

Sun Sep 01, 2013 9:56 am

Regarding item 2) I cannot see you achieving anything close to 120Mbps download speed as the LAN port on the Pi is only 100Mbps, and even that is likely to not be easily achievable because of USB overheads/limitations. The disk will also be using some of the USB bandwidth. I would have thought anything more than about 20-30Mbps sustained throughput is extremely hopeful (although I must admit I have never done any tests to prove what is achievable).

On item 3) you will also need a SD card to boot the system. If you are prepared to put the OS files onto a hard drive partition (by default the Pi runs from the SD card) then it can be a small one (at least 32MB), but otherwise it should be at least 4GB (and more might be desirable) - I tend to recommend 8GB as a good size at a reasonable price if you are not sure what you need.

mrgreaper
Posts: 42
Joined: Sat Aug 31, 2013 10:49 pm

Re: thinking of buying a pi need some advice

Sun Sep 01, 2013 3:16 pm

Cool, the speed issue which is my main concern, I should point out I explained it badly, over here in the uk the speed is called 120meg but it is not that fast in file transfer terms (there's a very geeky explanation along the line of bytes and bits but I can't remember it at mo) the actual speed of throughput is around 14 to 15 megs a second well bellow what you would get copying files over the lan network.. If I understand correctly you are saying that 20 to 30 is possible so 15 shouldn't be an issue?

W. H. Heydt
Posts: 10762
Joined: Fri Mar 09, 2012 7:36 pm
Location: Vallejo, CA (US)

Re: thinking of buying a pi need some advice

Sun Sep 01, 2013 4:00 pm

mrgreaper wrote:Cool, the speed issue which is my main concern, I should point out I explained it badly, over here in the uk the speed is called 120meg but it is not that fast in file transfer terms (there's a very geeky explanation along the line of bytes and bits but I can't remember it at mo) the actual speed of throughput is around 14 to 15 megs a second well bellow what you would get copying files over the lan network.. If I understand correctly you are saying that 20 to 30 is possible so 15 shouldn't be an issue?
I think part of what you're looking at on speeds is the difference between BITS per second and BYTES per second. Formally, (assuming a Mega- prefix), your line speed is expressed in bits per second: 120Mbs. Most people look at transfer speeds in Bytes per second, so the raw speed of that line is on the order of 12 MBs.

The other part of the issue is that, yes, some of the bandwidth is used for things like packet overhead (addresses and such) and protocol information, so you will never get the full quoted speed out of any data line.

The 100Mbs limitation of the Pis Ethernet is, indeed, lower than your 120 Mbs service. In addition, the Pi has to share that connection with its USB ports, so there is additional, internal, protocol overhead and there will be occasional packet collisions, especially if an active, relatively high data rate device is sharing the CPUs only USB channel. (Keyboards and mice don't really enter into this because they exchange very small amounts of data at--what is to a computer--relatively long intervals.)

Hope that helps without adding confusion.

itimpi
Posts: 1088
Joined: Sun Sep 25, 2011 11:44 am
Location: Potters Bar, United Kingdom
Contact: Website

Re: thinking of buying a pi need some advice

Mon Sep 02, 2013 6:23 am

The bits-per-second and bytes-per-second issue seems to confuse a lot of people!

I try and be consistent and use a lower case b for bits (e.g. 120Mbps) and upper case B for bytes (e.g. 15MBps). On that basis these two values mentioned by OP are different ways of stating the same thing as a byte is 8 bits (although I often assume a ratio of 10 to 1 as a good approximation and it also allows for network overheads).

As a general rule network speeds are quoted in bits-per-second while most people think of transfer speeds as bytes-per-second. As far as the OP is concerned it is definite that the Pi will come nowhere near fully utilising a 120Mbps Internet link. I would expect a maximum of something in the range of 20-25% of that bandwidth to be used by the Pi running flat out doing transfers.

ghans
Posts: 7871
Joined: Mon Dec 12, 2011 8:30 pm
Location: Germany

Re: thinking of buying a pi need some advice

Mon Sep 02, 2013 7:49 am

Note that there are currently no fast transcoding
mediaservers for the Pi. If the client only accepts certain
formats, make sure you content already is in one of those.
Transcoding on-the-fly is nearly impossible with the meagre
CPU.

GPU-based transcoders are pretty fast , but nowhere near
feature-complete.

ghans
• Don't like the board ? Missing features ? Change to the prosilver theme ! You can find it in your settings.
• Don't like to search the forum BEFORE posting 'cos it's useless ? Try googling : yoursearchtermshere site:raspberrypi.org

Return to “Beginners”