100Mbps Ethernet Speed/Efficiency
Joel Jaeggli
joelja at darkwing.uoregon.edu
Tue Apr 6 23:13:12 UTC 2004
On Tue, 6 Apr 2004, Neall wrote:
> On Tue, 6 Apr 2004 at 3:38pm, Joel Jaeggli <joelja at darkwing.uoregon.edu>...:
>
> > You can build a pretty wicked disk subsystem these days. single 15k rpm
> > disk-drives can read a rate of around 86-78MB/s depending on what part of
>
> Technology Marches on! My keeping up with it doesn't :)
>
> > Do the machines in question have the ethernet in 64 bit pci slots?
>
> It's an SBC, and ethernet is on board. The schematic shows an
> interconnect via 64-bit PCI-X, 133 MHz, via an Intel 82870P2 PCI/PCI-X
> hub. The eth chip itself is an Intel 82546EB. Dual Gigabit. Soldered
> in. Copper trace PCI, but no plug-in connectors.
>
> > block reads on 4GB files from a netap-940 we were testing were order of
> > 83MB/s using jumbo 9k ethernet frames... dropping that to 1500mtu made it
>
> Off topic (SORRY): Where do I tune these parameters in my NFS setup?
> I'm actually running RHEL WS3.0 (not Fedora) but should be similar.
mtu is actaully tuned on a per-interface basis. you want be be careful and
avoid situations where you might blackhole yourself talking to 1500mtu
devices on the same subnet, so generally when we want to use a 9k mtu we
do so on a private switch or in the case of our larger switches on a
private vlan.
just doing:
ifconfig ethX mtu 9000
on the interfaces you want to talk over is enough to get the ball rolling
assuming your switch support jumbo frames (not all do). a good cheap
switch which does is the smc SMC8508T which is < 1$60.
nfs is one of the few applications in our testing where we see a fairly
serious performance improvement in going to jumbo frames.
> > desktop which just has 100baset. For small switched environments where
> > performance is important unmanged gig copper switches now cost order of
> > $20 a port or less, so if you need the speed it may be cheap.
>
> Exactly, our plan is it run multiple SBCs but not have them communicate
> over a backplane. Instead, using an unmanaged, copper giga switch and
> Cat5E between them. :) Endpoints will be NFS-mounted RAM disks. You
> folks are demonstrating to me that it's a pretty efficient pipeline.
should be.
> Neall
>
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Joel Jaeggli Unix Consulting joelja at darkwing.uoregon.edu
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