Gigabit speed a scam?

Is gigabit a scam, or is there some hidden tuning you have to do?

On multiple machines (WinXPsp2 - WinXPsp2; Win2003sp1 - WinXPsp2,
Win2003sp1-Win2003sp1) with multiple brands of adapters I've never seen
throughput higer than 20% utilization on large (700mb) file copies. Some
are pci cards, some are integrated on the motherboard. None get close to
wire speed. Not even on smaller (25mb) files that fit complete in the disk
cache. They don't transer any faster on consecutive reads.

It's not pegging the cpu. It just won't transfer at the anything close to
wire speed.

That is how Ethernet always works. Nothing ever uses the full wire capacity for
a single session. If it did the network would jam up and quit working and only
two computers would ever be able to have a session with each other at the same
time.

Bandwidth is not "speed", it is how much data can move over the line in a given
period of time.

Throughput is the speed.

Using a road as an example:

Bandwidth = How many lanes the road has which effects how many cars can be on
the road at a given location.

Throughput = is the speed limit of the road

If the speed limit is 60mph, then a 4-lane road has twice the bandwidth of a two
lane road, while both run at the same 60mph speed,...but the 4-lane road moves
twice the number of cars over the same amount of time even though each car is
still only running 60mph.

However bandwidth and throughput are related,...I am not going to pretend to
know all the little gory nuances of it.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

The views expressed (as annoying as they are, and as stupid as they sound), are
my own and not those of my employer, or Microsoft, or anyone else associated
with me, including my cats.
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"Robert" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Is gigabit a scam, or is there some hidden tuning you have to do?
>
> On multiple machines (WinXPsp2 - WinXPsp2; Win2003sp1 - WinXPsp2,
> Win2003sp1-Win2003sp1) with multiple brands of adapters I've never seen
> throughput higer than 20% utilization on large (700mb) file copies. Some are
> pci cards, some are integrated on the motherboard. None get close to wire
> speed. Not even on smaller (25mb) files that fit complete in the disk cache.
> They don't transer any faster on consecutive reads.
>
> It's not pegging the cpu. It just won't transfer at the anything close to
> wire speed.
>
>

"Phillip Windell" <@.> wrote in message
news:%(E-Mail Removed)...
> That is how Ethernet always works. Nothing ever uses the full wire
> capacity for a single session. If it did the network would jam up and quit
> working and only two computers would ever be able to have a session with
> each other at the same time.

You are apprently too young to remeber 10mb ethernet, on hubs.

Any two computers would jam the network and achive ~70% through put. Where
the acks were causing collisions with the transmitted data.

100mb full duplex on a switch should be transfering at ~90% since it doenst'
step on itself.
This is what I routinoule see between any pair of computers.

>
> Bandwidth is not "speed", it is how much data can move over the line in a
> given period of time.
>
> Throughput is the speed.
>
> Using a road as an example:
>
> Bandwidth = How many lanes the road has which effects how many cars can be
> on the road at a given location.
>
> Throughput = is the speed limit of the road

That's a really bad analogy. Any pair of computers can use all of the
bandwidth (on a LAN, no latancy tcpwindow issues).

This is the whole point of a switched architecture - every car gets it's own
lane, no collisions like you got on hubs or thinnet with shared segements.

"Robert" <(E-Mail Removed)> wrote in message
news:%23%(E-Mail Removed)...
>
> "Phillip Windell" <@.> wrote in message
> news:%(E-Mail Removed)...
>> That is how Ethernet always works. Nothing ever uses the full wire capacity
>> for a single session. If it did the network would jam up and quit working and
>> only two computers would ever be able to have a session with each other at
>> the same time.
>
> You are apprently too young to remeber 10mb ethernet, on hubs.

I'll take that as a complement.
I been around since manual typewriters, mimiograph machines, teachers with
wooden paddles, and remember LBJ taking over for JFK.

> This is the whole point of a switched architecture - every car gets it's own
> lane, no collisions like you got on hubs or thinnet with shared segements.

Switched Full-Dup avoids having collisions and is a lot more efficient,...but it
still never gives 100% of the advertized speed of the wire,...there is too much
overhead both at the Ethernet level and the TCP/IP level. Switches even
introduce processing lag that the hubs don't have and also introduce other
overhead like ARP Table maintainence and STP that hubs don't have.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

The views expressed (as annoying as they are, and as stupid as they sound), are
my own and not those of my employer, or Microsoft, or anyone else associated
with me, including my cats.
-----------------------------------------------------