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Load Balancing across switches

Load Balancing across switches

We have:

2 ProCurve 5308XLs, both with one 1000Tx card (4 ports) and 7 10/100 cards.

2 ProLiant DL380s, which have 2 1000Tx ports each.

What's the best way to load balance across the switches? Am I best to connect all gigabit ports to one switch, and then use trunk routing via a couple of 10/100 connections to the second switch, or can I put one 1000Tx connection from each server into each switch (i.e. one "half" of the load balancing to each ProCurve) and load balance that way?

Meshing doesn't seem to be an option as we need IP routing on the switch.

TIA.
8 REPLIES
Ralph Bean_2
Trusted Contributor

Re: Load Balancing across switches

Hi Kenny -

You can't use trunking to connect multiple NICs in a PC to multiple switches. You will need to consider some sort of teaming solution. If you are not familiar with teaming, see www.vmware.com/pdf/esx2_NIC_Teaming.pdf.

Regards,
Ralph

Re: Load Balancing across switches

Hi Ralph,

Thanks for the reply. I'm not sure I've made myself clear, so let me clarify:

The two switches will be connected together by trunking - a cable from one gigabit port to another.

Each server - there are two - has two gigabit ports. They are configured as load-balanced, and appear to Windows 2003 as a single network connection with a single IP address, giving 2Gb/s.

I can plug the two cables from each server into the first switch, but that means devices on the second switch have to cross the trunk to get to the server. (A very minor thing, I know, but I'm a perfectionist :)

What I'd like to two is plug one cable from each server into each switch - so there's one "half" of the single load-balanced connection on each switch. That way the server will load-balance across the two switches - i.e. a device on switch 2 will be able to access the server directly without having to cross the trunk route. Is this possible?

Ralph Bean_2
Trusted Contributor

Re: Load Balancing across switches

Hi Kenny -

You wrote, "They are configured as load-balanced...". What software supports this load-balancing on your PC? Windows? Netware INETCFG? ProLiant teaming? other?

I think your overall question boils down to: does your team software support connections to multiple switches? I can imagine various ways that teaming software could work.

Regards,
Ralph

Re: Load Balancing across switches

Hi Ralph,

We're using the HP-supplied teaming network drivers as supplied in the Proliant support software. On the NetWare server, this is based around QASP.NLM, and on Windows it's CPQTEAM.SYS. Does this help?

Cheers

Kenny
Ralph Bean_2
Trusted Contributor

Re: Load Balancing across switches

Hi Kenny -

I am not familiar with how your two teaming methods work. Do H-P and Novell's provide any documentation (for example, an application note) regarding whether they recommend you connect a PC to multiple switches?

Regards,
Ralph
STEVEN LEE_12
Frequent Advisor

Re: Load Balancing across switches

The NICs on the servers provide teaming function which is a form of load-balancing.

Since the switches are trunked using a special gigabit cable, there is really little use to try to further load-balance the switches as they perform as a single switch, without performance degradation, whether physical connections are made to the 1st or 2nd switch.

You should not think and see the switches not as 2 separate devices but as one. Although the switches are separate physically, the network sees them as 1 logical switch.
Stuart Teo
Trusted Contributor

Re: Load Balancing across switches

Hi Kenny,

From your statement "Each server - there are two - has two gigabit ports. They are configured as load-balanced, and appear to Windows 2003 as a single network connection with a single IP address, giving 2Gb/s."

It seems that the 2 x gigabit in each server are being trunked to become a single link. There are several ways I know of that can achieve that: FEC aka PAgP, IEEE's LACP and the third and last simplying called TRUNK.

The different is in how the driver behave.

TRUNK= server will assume that switch is trunk capable and will start to trunk upon startup.

FEC= server will use PAgP, cisco's propietary protocol, to negotiate a trunk with the switch.

LACP= server will use LACP, a IEEE standard, to negotiate a trunk with the switch.

Whichever it is, both links must be plugged into the SAME SWITCH. UNLESS the 2 switches are stacked into a single logical switch using the STACKING KIT. Not all models support stacking. The 4000m has stacking capability but I don't recall the 5300xl to have the stacking capability.

If you put the 2 links into 2 different switch, it will appear to work as long as you don't saturate the 1st link. Once you saturate the 1st link, your network will start getting confused.
If a problem can be fixed, there's nothing to worry. If a problem can't be fixed, worrying ain't gonna help. Bottom line: don't worry.
OLARU Dan
Trusted Contributor

Re: Load Balancing across switches

Put each server in a different switch and do a GEC between switches.


SW1===GEC===SW2
||<-----teaming----->||
SRV1.....................SRV2

This will occupy all Gigabit ports on the modules in both switches. At this speed between switches, the physical location of the servers does not matter.