[Sderby] Gigabit ethernet

[David Jolley]

>Does anyone want to hazard a guess at what sort of CPU and memory would be 
>required to saturate 1, 2 and 3 gigabit interfaces in a Linux NFS server?
>

Mike,

A gigabit ethernet adapter is perfectly capable of saturating a PCI bus;
It's highly unlikely that the processor's going to be the bottleneck in the
system, unless you have a high-end (high end server class, certainly - I've
not seen any consumer grade mobos with this PCI bus configuration)
motherboard with pretty much every motherboard component on it's own PCI bus
hung off a backplane PCI switch with an enourmous amount of bandwidth
available to it.  Even with this bus topology available to one gigabit
ethernet interface, the processor will have to shunt data from somewhere, so
you may need something in the range of a 2 Gig processor, and one with
plenty of MHz on it's FSB, to boot.  To find a motherboard with 3 separate
PCI busses available to PCI expansion cards (your 3 gigabit ethernet NICs)
is a real achievement.  Then saturating *1* gigabit ethernet card is your
next problem.  Saturating two I would suggest is unlikely with 3 being next
to impossible, just because of the sheer volume of data being shunted round
the system.  Find a motherboard with at least 6Gbit/S backplane (3*1Gb NIC *
2 as the data must come from somewhere) bandwidth, at least 6 unbridged PCI
busses (3 for the NICs and 3 for the devices supplying them individually
with data - I'm not going to go into whether a hard disk that's not a RAID
cluster will be able to sustain a high enough data rate), and a processor
with at least 7Gbit/S bandwidth available to it (it's got to shift the data
to the NIC from somewhere, plus run code - this may be overkill if the NICs
and the Hard Disks can act as DMA targets and masters respectively; and
you'll be *really* lucky if the PCI->PCI DMA transfer will work - we've had
all sorts of problems with this at work) and you'll have a system capable of
saturating the 3 Gbit NICs.  In other words, and IMHO,  you're not going to
do it in PC class (off the shelf, anyway) hardware.

Cheers

Dave.