sje
Posts: 13
Joined: Sat Dec 24, 2011 4:15 pm

Re: Bramble cost estimates

Thu Dec 29, 2011 6:29 am

Bramble cost estimates:

Raspberry Pi Bramble node components and costs:

1) RP Model B (256 MB RAM, 10/100 Mbps NIC) $35

2) Wall wart power supply $ 5

3) 4 GB Compact Flash card $13

4) DIY Cat 5 Ethernet cable $ 2

5) One port on a Fast Ethernet switch $ 7

6) Mounting hardware $ 3

Total per node: $65

Bramble ( 2 nodes): $ 130 ( 1.4 CHz)

Bramble ( 4 nodes): $ 260 ( 2.8 GHz)

Bramble ( 8 nodes): $ 520 ( 5.6 GHz)

Bramble (16 nodes): $1,040 (11.2 GHz)

Bramble (32 nodes): $2,080 (22.4 GHz)

Bramble (64 nodes): $4,160 (44.8 GHz)

foo
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Re: Bramble cost estimates

Thu Dec 29, 2011 6:39 am

2) You shouldn't use a power supply per node if you're clustering; grab a bigger power supply and wire it to a number of nodes.

3) Compact Flash?  You should be looking for SD Cards.  They're around $5 each on amazon, probably less if you can score them bulk.

4) $0.99 each at Fry's Electronics, if you've got one around.

5) You sure you're looking at "Fast Ethernet", aka 100Mbps, and not 1000Mbps?  This should be more around $3 in a 16-port 100Mbps switch.

ghans
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Re: Bramble cost estimates

Thu Dec 29, 2011 3:05 pm

Isn"t difficult to estimate the computing power of a cluster ? Can you just add up clock speed of each node ?

ghans
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Gert van Loo
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Re: Bramble cost estimates

Thu Dec 29, 2011 7:54 pm

I think it mostly depends on what you want to achieve.

What I have seen form other posts is that the Raspberry-Pi is not the right machine if you want to have the highest number if MIPS per buck.

However if you look at the MIPS per watt I think the Raspberry-Pi is probably far ahead of anybody else. ( >24Gflops/sec for about 1 watt)

As to building a bramble:

It is possible to connect the devices using the CSI/DSI ports. That gives you theoretical 4Gbits/sec. But the protocol overhead and the synchronization would half that. Still 2 Gbits/sec is not too bad.  There are 2:1 multiplexers available for those links (Fairchild) and that again would allow you to make a mesh of devices.

Just a direct link would require special CSI and DSI drivers for the GPU and is several man-months work. Building a good protocol over a mesh: I would say two man years.

Warringer
Posts: 56
Joined: Tue Aug 23, 2011 5:04 pm

Re: Bramble cost estimates

Thu Dec 29, 2011 8:25 pm

2 + 6) Build yourself a GPIO bus with angled connectors. Say eight of them on a single cheap experimental PCBs with only the 5V and GND pins actually connected to something. Combine it with the CAT 5 cables and you should have a rather stable mount as long as you don't shake them around. Maybe some holes in the Bus PCB and some zip ties for additional stability.

3) You don't even need 4GD per Pi. 1 GB should be more then enough. Or get a couple of old 16 to 32 MB SDs in bulk and then with a bootloader load the OS from the network.

4) Get a good length of cheap CAT5 cable and CAT5 connectors en bulk. Or a cheap 5+ meter cable and single CAT5 connectors. Some hardware stores should sell those CAT 5 connectors for two or three Dollar per ten pieces.

5) @foo: The Pi can only handle Fast Ethernet.

sje
Posts: 13
Joined: Sat Dec 24, 2011 4:15 pm

Re: Bramble cost estimates

Fri Dec 30, 2011 12:54 pm

Second pass:

1) SDHC 8 GB

From $8 to $16 depending on class and brand with possible quantity discounts.  For some applications, lesser capacity cards just don't have the storage capacity and aren't that much cheaper anyway.  Question: Can an RP handle a class 10 SDHC?  One source says no.  Question: Are there warnings aganst using particular brands or models?

2) Ethernet switches

One idea is to use 100 Mbps switches at the bottom tier with 1000Mbps switches at higher tiers.  Each bottom tier switch could be a five port unit which connects four RP plus one link to the next higher tier switch.  For some applications, a less expensive five port hub could be substituted for the bottom tier switch.  The uppermost tier connects to a controlling workstation.

3) Wall warts

A mini USB wall wart is cheap and using one means not having to build cabling and solder connections.  The alternative of having a single, large power supply just increases the chance of having a single point failure which can wipe out the entire cluster permanently.  Wall warts can be plugged into a power strip which in turn has built-in surge protection.  Bonus: some power strings also have in/out Ethernet surge suppression jacks.  Wall wart alternative: Power the entire cluster with a large capacity 6 volt motorcycle battery.

4) Plexiglass mounting frame

The idea here is to build a plexiglass frame and drill holes in the frame for a custom metal/plastic mount for each RP.  For my application, it would be useful to bulid the clunter eight RP at a time, so the frame could hold eight boards and be later connected with other frames.  All cabling would be secured via stress relief palstic wrap strips which in turn are threaded through hole pairs drilled in the frame.  The entire assembly should be light enough for mounting on a wall.

5) Blinking lights

Each RP has some number (how many?) status LEDs and these should be visible after the beard s are mounted in the frame.  A more general approach would be to use some commercial LED displays (8 to 64 LEDs each) and have these mounted on the frame and wired to the GPIO pins.  Related: Each RP could drive an inexpensive 2x16 character LCD mounted on the frame.

Prometheus
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Re: Bramble cost estimates

Fri Dec 30, 2011 1:16 pm

sje said:


Question: Are there warnings aganst using particular brands or models?


Whilst I don't know how certain brands and models work with the RPi*, it's certainly worth avoiding certain outlets for purchasing SD Cards.

*That said, my past experience with other platforms has been that it's worth going with a manufacturer like SanDisk who makes all of their own parts, rather than inconsistent restickering brands like Kingston, where cards that are ostensibly the same don't have the same guts, and thus won't necessarily perform the same.

david13lt
Posts: 20
Joined: Thu Sep 08, 2011 4:55 am

Re: Bramble cost estimates

Fri Dec 30, 2011 1:42 pm

If it is possible drop SDHC from your list. Use networked storage and networked boot. This is gonna save time and money. Nodes are pure computational nodes. Nodes would be easy updatable with the latest software just by doing restart on each node. Node can be lost, but the storage is never lost.

sje
Posts: 13
Joined: Sat Dec 24, 2011 4:15 pm

Re: Bramble cost estimates

Fri Dec 30, 2011 1:49 pm

davidlt said:


If it is possible drop SDHC from your list. Use networked storage and networked boot.


Alas, my application set needs to have a significant amount of local data with frequent accessing and trying to support such over a net is impractical.

foo
Posts: 52
Joined: Thu Dec 29, 2011 12:49 am

Re: Bramble cost estimates

Sat Dec 31, 2011 6:51 am

As far as things have been described, you cannot do pure network boot without local storage.  You need to hit the SD card first, and have it do the netboot.

darkstar
Posts: 29
Joined: Wed Dec 28, 2011 4:20 pm

Re: Bramble cost estimates

Sat Dec 31, 2011 8:43 am

foo said:


As far as things have been described, you cannot do pure network boot without local storage.  You need to hit the SD card first, and have it do the netboot.



You can have the best of both worlds: SD card does netboot and the rest of the space is scratch storage.

Because of the design of the R-Pi you have to have the SD card for booting. It loads the binary off the FAT partition and then passes control to the next partition (EXT2 (with/without knobs on) to get the boot image. This one can be a netboot. So it then sucks the remaining binary over cat5.

Your application then NFS/Samba's its data from some external storage, if necessary, and stores it temporarily on the remaining SD. When it has finished it returns the answers to the more respectable host and deletes the scratch.

Depending on how you want to do it you could either have scratch in a separate directory or give it a whole new partition. Presumably the R-Pi won't get confused by 3 partitions (?).

jamesh
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Re: Bramble cost estimates

Sat Dec 31, 2011 9:51 am

darkstar said:


foo said:


As far as things have been described, you cannot do pure network boot without local storage.  You need to hit the SD card first, and have it do the netboot.


You can have the best of both worlds: SD card does netboot and the rest of the space is scratch storage.

Because of the design of the R-Pi you have to have the SD card for booting. It loads the binary off the FAT partition and then passes control to the next partition (EXT2 (with/without knobs on) to get the boot image. This one can be a netboot. So it then sucks the remaining binary over cat5.

Your application then NFS/Samba's its data from some external storage, if necessary, and stores it temporarily on the remaining SD. When it has finished it returns the answers to the more respectable host and deletes the scratch.

Depending on how you want to do it you could either have scratch in a separate directory or give it a whole new partition. Presumably the R-Pi won't get confused by 3 partitions (?).


Three partitions is fine.
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