[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: 2 Network Cards

On Fri, Feb 01, 2008 at 07:28:47PM -0800, Raquel wrote:
> On Fri, 1 Feb 2008 21:54:37 -0500
> "Douglas A. Tutty" <dtutty@porchlight.ca> wrote:
> > On Fri, Feb 01, 2008 at 06:37:04PM -0800, Raquel wrote:
> >  
> > > Thanks, Doug.  Yes.  The "9"s are place-holders.  I've not been
> > > using the second nic because it wasn't needed.  However, now I
> > > want to host 2 different SSL hosts using named virtual hosts.
> > > So, I need a second IP and I'm dipping into my range of IP
> > > numbers.
> > 
> > If they truely are on the same physical pice of wire, why not use
> > virtual/aliases.  Eg, instead of eth0 and eth1, you would have eth0
> > and eth0:1 or something (never done it, check the man pages).
> Don't I end up doing the same thing?  I thought of aliasing eth0, but
> why?  I have a nic not being used in the machine and running another
> wire from my switch to it will give me what I need.  If I alias eth0
> to eth0:1 I'd still need to assign eth0:1 another IP number. Right?

Sure.  It would make sense if the hardware could keep up with two NICs
going full-out, so it depends on the network speed (10/100/1000), the
speed and quality of the NICs, and the power of the computer.  Either
way, every packet has to go through the kernel and the firewall code.  I
don't know which is faster.  It takes a monster of a box to keep a GB
ethernet saturated, yet alone 2.

Look at it this way:

Lets say we're dealing with a 100 MB/s ethernet.  Lets say that all the
boxes on the network are all capable of saturating their 100 MB/s
ethernet.  If all the NICs all try to talk at once, as long as they are
talking in pairs, then the switch should handle it.  In this case,
having two NICs in your box makes sense because, being two virtual
boxes, it is conceivable that two different client boxes will want to
talk to the server box at full speed, as long as the server box can keep
2 100 MB/s NICs well fed while doing the serving.  Also, as long as the
switch back-plane has the throughput.  

Remember, a second NIC will mean twice the hardware to be interrupting
the CPU.  

I would rather spend the money on one good NIC than two cheaper ones.  


Reply to: