Members of the ISP-Webhosting list discuss getting better performance out of an existing server by adding Ethernet cards. Results will depend on the operating system used and the network configuration.

[June 27, 2001]

On the ISP-Webhosting list in June, PP queried,

"What are the advantages or disadvantages of placing multiple (two or more) Ethernet cards in one web hosting machine? Up until now I've used only one per machine, but the folks I'm going to be buying some machines from say to stick more Ethernet cards in the darn things."

A number of respondents suggested that there are lots of reasons for doing so:

[AH advised] "They're used primarily for redundancy. Should one card fail, you can have the other kick in. Other uses include load balancing network links (two upstreams, two separate IPs). With two cards, you can change the way things function, including routing to certain hosted sites, etc. I have never seen a use for more than two cards, but that doesn't mean they don't exist."

[DS added] "If you're using Linux, you can do a number of things.

• You can bond multiple Ethernet cards together for more bandwidth in and out of the server (see Don Becker's work on Beowulf network drivers here).
• You can use extra cards as fault tolerant failovers (see the work being done at the High-Availability Linux Project).
• You can assign different IP addresses to each card for various reasons.

And no matter what OS you use, you can make one or more cards face the Internet and one or more cards face a private network. You could use this, for example, if you were going to store credit card numbers in a database: it's risky to hang any machine that has credit card information directly on the Internet."

[SH noted] "We use them for load balancing and redundancy to the upstream IP network. In addition, if you are using NAS as the primary data store, it's not a good idea to have that traffic on the same physical segment for security, performance, and manageability."

DN added a new layer to the discussion:

"Along these lines, has anyone had any success binding multiple Ethernet cards together on an NT machine? I wanted to add an Ethernet card to an NT server that is having slow database response times. I don't know if I can make a fatter pipe using multiple NICs on NT. The problem is, if I assign an additional IP to the second NIC card, I don't think the assorted Win98 clients connecting to it would even notice the new card. Any advice?"

DK suggested that adding more cards is unlikely to solve the problem:

"Response time typically has nothing to do with the size of the pipe when it comes to database applications. If your single Ethernet card is saturated, that could affect response time a little, but I doubt that is the case here.

One way to test whether or not it is a network issue is to ping the database server from one of the client boxes. If the pings are coming back in under a millisecond or so, it isn't a network issue. If you want to get better response time, you may need to upgrade your server, set up a secondary database server, or perhaps rewrite the database schema or queries to make them more efficient."

—End