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Mixing Gigabit, Copper, and Linux
iampgray writes: "With copper-based gigabit cards selling for less than $36 these days, what kind of performance can you expect -- especially in the often-overlooked Linux market? We sought out to test exactly what you could expect from copper-based gigabit solutoins for the desktop interface through the cluster-targeted products. Name brands and off-brands were put through the wringer. How'd they fare? Interesting results to say the least."
I checked out the cards, and yes you can get them cheap, but what about switches? You figure they're still uber-pricey too, right?
:)
Nope... apparently Pricewatch.com has D-Link 8-port 10/100/1000baseT auto-detect switches listed for under $150! (I've been most happy with my D-Link DI-804 Router/firewall/switch for $79.)
Is this the normal "cheaper as tech gets more widespread and easier to manufacture," and do you think maybe Apple making gigabit ethernet a standard feature had something to do with it?
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Note: When connecting a Power Mac G4 computer directly to another computer without using an Ethernet hub, a crossover cable is not required; circuits in the PHY detect the type of connection and switch the signal configuration as required.
Are we even to the point when a normal PC could handle Gigabyte? And if so, why not use optical?
A 32-bit 33 MHz PCI bus can support one (1) gigabit ethernet card at full capacity (card's bandwidth is about 100 Mbytes/sec, PCI 32/33 is 133 Mbytes/sec).
If you want to stick multiple cards in (e.g. for a small hypercube-style cluster), buy motherboards that support 64/33 or 64/66 (I was drooling over the dual-processor 64-bit-PCI AMD boards a little while back).
Gigabit ethernet over copper has the advantage of running over your existing cabling (i.e. cat-5 is fine). This avoids having to muck about with fiber, as fiber is a PITA to maintain yourself (getting optically perfect connections for the fiber jacks is picky).
The way gigabit ethernet is encoded on cat-5 cable is both sneaky and elegant.
A 32-bit 33 MHz PCI bus can support one (1) gigabit ethernet card at full capacity (card's bandwidth is about 100 Mbytes/sec, PCI 32/33 is 133 Mbytes/sec).
Almost. 133MBytes/sec = 1064Mbit/sec. This means that it could only in theory keep up, if all bandwidth on the PCI bus was available for data. But, this number includes the overhead of setting up transfers and arbiting for devices that want to transfer, and these operations are fairly expensive.
Also, the PCI device needs to obtain descriptors etc. (which indicate where to put the Ethernet packets in RAM) over the same bus, costing more valueable cycles.
If you did have only the one device on the PCI bus (which is very unlikely), with a good chipset, you'd probably get over 100MB/sec, but not much more. So you'd never be able to actually get full Gb Ethernet. (as the test results show, things are MUCH worse then this, but this is probably caused by multiple devices on the PCI bus).
Talking about chipsets, a long time ago we had a board with an OPTi chipset. They ran out of silicon when designing the chip, so they couldn't implement the Bus Master FIFO, so they decided to just abort every BM cycle after each 32 bit transfer, yielding a max transfer rate of 4MB/sec!! For weeks, I couldn't figure why my network driver wouldn't send packets faster than 30 Mbit/sec, until my boss flew to California (where OPTi was located) to find out what we where doing wrong.
Back to the tests: for some reason they failed to mention the chipsets used on the motherboards which really is VERY important if you want to use a gigabit Ethernet card in a 32/33 PCI system. The fact that the Dell has 5 PCI slots probably means that it has an integrated PCI-PCI bus (not many chipsets support 5 PCI slots, unless one or more of them do not support Bus Mastering), which would certainly not improve things.
I think this is important to mention, because most systems today, at least desktops, will only have 32/33 PCI, and as the test results show, with a presumably shitty chipset, you only get marginally better performance than 100Mb Ethernet...
If that was so easy for you to do, don't you think it's been done?