[Arm-netbook] EOMA server standard

[Gordan Bobic]

On 10/24/2012 01:14 PM, luke.leighton wrote:
> On Wed, Oct 24, 2012 at 8:53 AM, Gordan Bobic<gordan at bobich.net>  wrote:
>> On 10/23/2012 06:09 PM, luke.leighton wrote:
>>> ok, right.  i've been talking to some companies and the need for a
>>> standard which covers data centres - e.g. has 10Gigabit Ethernet - has
>>> come up.
>>>
>>> it turns out that 10GBase-T is 500mhz and 16-way PAM over each of the
>>> 2-twisted-pairs that go onto a standard RJ-45.  so, *fast*, but also
>>> staggeringly power-hungry.  this 10GBase-T PHY IC has one variant at
>>> 2.4 watts and another at 6 watts:
>>>      http://www.solarflare.com/Ethernet-Controllers-LOMs
>>>
>>> so the question i'm raising is: what would people see as being the
>>> most appropriate general-purpose and lowest-common-denominator
>>> "upgradeable" interfaces to have on an EOMA standard?  and, what case
>>> would be good to re-use?
>>>
>>> for the pin-outs i figured that at least one 10GBase-T interface (8
>>> pins plus 8 GND spacers) would be acceptable, as would SATA-3 (4 pins
>>> plus 4 GND spacers).  that's 24 pins already (!).  PCI-Express 4x is
>>> 64 pins.  that's up to 88 *already*.  adding in USB3, it's not
>>> unreasonable to imagine this would be a 100-pin standard.
>>>
>>> so this is going to need some really careful thought.
>>
>> Why on earth would anyone in the right state of mind even consider
>> running 10G ethernet over copper?
>
>   *lol* i don't know!  preexisting infrastructure (racks) maybe?

This has nothing to do with racks, it's to do with switches.

>> Every deployment I have seen to date is fibre based. 10G copper switches don't sound particularly plausible
>> if you have to vent out 6W of heat per port.
>
>   that makes sense.  yeah.  5W processor; an extra 6W on the port.  duh.

Multiply by 48 for a decent sized switch and it rapidly gets to the 
point where most of he mass of the switch becomes fans and heatsinks. 
10G copper just isn't practical.

>> If fibre is not an option for the chassis for some obscure reason,
>> multiple gigabit connections (you have to have a built in gigabit switch
>> anyway for each node) are a much more sensible option than 10Gb copper,
>> and much cheaper and more versatile than fibre.
>
>   hmmm...  ok.  that makes sense.  thanks gordan.

Possibly the best option might be a single 10G fibre port with 
additional 4-5 copper gigabit ports for people who aren't set up for fibre.

Gordan