NLB - When to use?

cbriant

Hi,

In the practice exam scenarios that I have come across, it appears that NLB clustering is generally only used for web servers. Are there any other applications of NLB clustering?

Chris.

Mishra

Exchange also uses NLB. Quite a few other off brand applications let you use NLB. It's a good skill to know.

royal

Office Communication Server 2007 also uses NLB. The only difference here is you need to use hardware load balancers for OCS, not Windows NLB.

donald7862003

Mishra wrote:

Exchange also uses NLB. Quite a few other off brand applications let you use NLB. It's a good skill to know.

I thought that NLB wasnt good for exchange because the information isnt static like a web server.

Mishra

donald7862003 wrote:

Mishra wrote:

Exchange also uses NLB. Quite a few other off brand applications let you use NLB. It's a good skill to know.

I thought that NLB wasnt good for exchange because the information isnt static like a web server.

I'm a little confused by "isn't static" so I might be off in my explanation. But mail traffic is very similar and uses the same ports all the time. If you have 2 spam servers taking in mail and distributing it to your front end Exchange servers then putting in the NLB IP for the mail direction in the spam servers is a good idea. I know some spam servers have distribution capability but its best to just let NLB work out the load balancing.

NLB also worked well for OWA traffic going into your front end servers.

donald7862003

I am sorry meant "Stateless" NLB would be great for VPN and web servers because that info does not change as much. Where as an exchange server would have to replicate information between the load balanced servers. example

If i had three servers (exchange) and i had info on one server and not the other if the request goes to the server that does not have the info then the request would be dropped or denied. Because web servers generally host the same info if a request goes to either server the request would be serviced. Exchange would be great on a cluster because clusters share drives (SCSI, Fiber)

dynamik

NLB is used for static content/services that rarely, or doesn't, change.

Clustering is used for dynamic content/services that changes frequently and requires shared storage.

For example, you'd use NLB on your web servers and clustering on your SQL and Exchange servers. Just think about the type of content and whether or not they require shared storage. So in the example I just listed, it wouldn't be a big deal to copy html/php/asp files to the local HDs for a few web servers whenever there was an update to the website, but there is no way something like that would be feasible with a database (SQL) server.

Mishra

Okay I think I see where you are thinking.

You wouldn't use NLB on your back-end exchange servers that do all the processing. You would setup front end servers that use NLB to direct mail traffic.

There are many advantages like security, single namespace, OWA, RPC for using the front end servers.

donald7862003

Mishra wrote:

Okay I think I see where you are thinking.

You wouldn't use NLB on your back-end exchange servers that do all the processing. You would setup front end servers that use NLB to direct mail traffic.

There are many advantages like security, single namespace, OWA, RPC for using the front end servers.

Okay I see what you are saying

donald7862003

donald7862003 wrote:

Mishra wrote:

Okay I think I see where you are thinking.

You wouldn't use NLB on your back-end exchange servers that do all the processing. You would setup front end servers that use NLB to direct mail traffic.

There are many advantages like security, single namespace, OWA, RPC for using the front end servers.

Okay I see what you are saying

Could you also explain how that would work? Front end servers fowarding mail traffic using NLB. I cant see it in my head how i would set that up thanks

Mishra

donald7862003 wrote:

donald7862003 wrote:

Mishra wrote:

Okay I think I see where you are thinking.

You wouldn't use NLB on your back-end exchange servers that do all the processing. You would setup front end servers that use NLB to direct mail traffic.

There are many advantages like security, single namespace, OWA, RPC for using the front end servers.

Okay I see what you are saying

Could you also explain how that would work? Front end servers fowarding mail traffic using NLB. I cant see it in my head how i would set that up thanks

Take a look at "Front-End and Back-End Server Topology Guide for Microsoft Exchange Server 2003 ". It's a pretty good guide with lots of information.

royal

Think of NLB as load balancing traffic. You send data to 1 IP, nodes will talk amongst themselves and distribute traffic accordingly. It is constantly load balancing traffic at all time so 1 node is not getting hammered.

With Microsoft Clustering Services (MSCS), it's not actively load balancing traffic. The closest to that would be an active/active cluster but they're not talking amongst themselves to load balancing traffic. Exchange/SQL/etc would be constantly talking to the same node, and if that cluster node dies, it'll fail over to the other cluster node.

I don't really look at the whole static vs dynamic content thing. I look at more of the load balancing traffic in real time (NLB) vs hardware failover (MSCS) to provide fault tolerance and provide minimal unscheduled downtime.

doom969

You can also use NLB with ISA. (you need to use affinity.)
You combine that with carp and you got yourself a pretty tolerant and load balanced gateway/firewall.

Its actually pretty sweet, you can also use it to balanc your traffic between 2 outgoing internet connections.

ISA is one of the product where nlb integrates really well.