GigE on ES4x servers

[Bryan J. Smith <b.j.smith@ieee.org>]

From: Balint Cristian <rezso at rdsor.ro>
> Realtek 8169 chipset based cards are cheap [~20USD], under 2.6
> kernel work very ok even on alphas [tested personaly]they are even
> NAPI capable and can move as good as an intel class card for e.g.
> As i know they work even with rechentisher 2.4.X kernel well
> [untested by myself].

Cheap GbE cards tend to have a very small amount (typically 32KB or less)
of SRAM.  Assuming 1500 byte standard frames, with only 32KB, the card
has to process 21 frames within every 40 microseconds.
At a bare minimum, a GbE card -- at least one on a server -- should
support 802.3x for congestion control.

> I talked about copper solution, dont see fiber for what is good instead 
> of copper if you have no more than 20m cable patches. Really.

EMI.  You should have more than a dozen Cat-5e/6 runs within a cubic
meter of volume.  Fiber is what you want to use in a closet, for sure.

> I was able to switch 800Mbit at high pkt/s through realtek without
> problem performing simple routing.
> Dont know other cheaper card, but on fiber there are intel cards even in 
> PCI-X form [e1000 driver], very good and reliable, even multiport forms on 
> single card solutions are from intel, booth single/multimod solutions.

Some of Intel's higher-end cards have a 256KB SRAM cache dedicated to
just reception.  I consider that the "bare minimum" on a GbE card when
you are concerned about performance.

And anything lacking 802.3x without a large SRAM cache is asking for
massive performance issues.

--
Bryan J. Smith   mailto:b.j.smith at ieee.org