[Samba] Samba and Multiple NICs

Clint Sharp clint at typhoon.org
Wed Apr 7 07:57:36 GMT 2004

On Mon, 2004-04-05 at 06:06, AndyLiebman at aol.com wrote:
> Clint, 
> Thanks for your reply. 
> What I want to do is straightforward in concept (perhaps difficult in 
> practice, though I doubt it). 
> I want to put two Gigabit Ethernet Cards in one Linux server -- and have each 
> card talk to half the Windows workstations in my place. In part, I'm looking 
> for a way to get more data in and out of my server (the storage part can 
> support it). Each workstation is running a video editing application and it's 
> looking for about 4 to 4.5 MB/sec of data. The data is time critical. It HAS to 
> arrive when needed, or the editing application stops. So far I'm doing okay with 
> just one network segment, but I think I can add a few additional workstations 
> if I split the network -- because my storage subsystem is capable of doing 
> well over 100 MB/sec -- and that's a lot more than I'm going to push down one 
> Gigabit Ethernet pipe. 
> In part, I want to configure the two Ethernet cards differently so that one 
> can talk to workstations that are optimized for "Gigabit Ethernet and Jumbo 
> Frames" and the other can talk to workstations that only have "normal Ethernet" 
> capabilities. 
> I'm NOT looking to get more data to a single workstation. I'm looking to get 
> the maximum number of workstations that can all receive the 4 to 4.5 MB/sec 
> that they need. 
> By the way, my Server hardware is: 
> 3.06 Ghz single processor Xeon, 1 GB RAM, Intel Gigabit nics, fast RAID 
> arrays, two switches capable of supporting Jumbo Frames. 
> Andy


This describes your network a bit better.  I think Samba probably
handles a multi-homed domain master browser much better than Windows, as
a quick search has not revealed problems with joining browse lists from
multiple subnets on a domain controller (this is a major problem with
Windows 2000, one I fought for quite some time and ended up having to
purchase additional hardware to solve, by moving the domain controller
to a dedicated single homed box).  This is good, as it shouldn't break
network browsing on a subnetted network with a multi-homed domain
controller (I'm assuming, maybe incorrectly, that Samba is your DC) like
Windows does.

Firstly, the machine will exist twice in WINS.  As long as there are no
routers between your clients (and you're indicating they're not, based
on your support for GigE and jumbo frames) you should be fine, seeing as
WINS client resolution will choose a name returned from a multi-homed
WINS entry on it's local subnet over another not in it's subnet, where
as a multi-homed machine not on the subnet chooses an IP at random, see
http://www.pmg.com/tip_archive/01_11.htm).  However, you might want to
give consideration to any clients which might be accessing this from
beyond the router (although it appears from your description of your
setup that you have one LAN connected to the Internet, so it seems
pretty simple)

However, secondly, I think you need to give consideration to how you're
going to implement Internet routing and routing between the different
subnets/VLANs as well as DHCP.  The easiest way to set this up is to
setup separate VLANs for the jumbo and non-jumbo frames and trunk
between your switches, this way switching a connection from jumbo to
standard framing is just a matter of changing the VLAN you're on. 
However, if your Samba server is not also your DHCP server, and your
DHCP is also not multi-homed, you'll need to implement a dhcp relay,
probably at the router level.  Also, you'll want to make sure your
router supports trunking 802.1q VLANs (or whatever proprietary VLANs
your switch might support) or has multiple Ethernet interfaces.  Keep in
mind all traffic not destined for the Samba server will flow through
this Router, and it will become a bottleneck for you.

If you have little traffic going machine to machine, I think this would
probably be a good solution for you, but I'd seriously consider the
amount of machine to machine traffic you have that will cross subnets,
as while you may gain increased performance from your fileserver, you
may kill network performance for other peer to peer file copies etc. 
Something to seriously consider, but I think Samba should accommodate
your situation quite well (better than Windows probably!).


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