Load Balancing SSAS Servers

Hello,

We are trying to load balance a pair of SQL Server 2005 Analysis Services query servers using hardware load balancing (Foundry switches) but we don't seem to be able to get it to work.

The main problem as far as I can tell is that we can't get the SSAS instances to listen on the IP address of the loopback adapter which is configured on both servers.

The netstat -ano command shows that the SSAS instances are only listening on the IP address of the physical NIC in each machine.

We are using a custom port and I can see where this custom port is defined in the msmdsrv.ini file but I can't see anywhere where you can tell SSAS the IP addresses on which to listen.

Should SSAS listen on all available IP addresses when it starts up ? We have re-booted both boxes but this hasn't made any difference ?

Can anyone shed some light on this please ?

Regards,

Paul Lynch

Hi Paul, I have not done anything like this before, so this is a bit of a long shot. I was wondering if the security setting that you need to change in order to use application names might need to be changed. see http://support.microsoft.com/kb/888526 - this article is for AS2000, but I think the same approach still applies for AS2k5.

I think by default it checks that the name/ip address match each other, so this may help.

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Hi Darren,

Thanks for your reply.

We actually found the problem - the network guy had forgotten to configure something called Direct Server Return (DSR) on the Foundry so the traffic wasn't being forwarded properly to the SSAS boxes. When I looked into it again I realised that the SSAS process was actually listening on the loopback adapter address as well as the IP address of the physical NIC so the problem wasn't what I originally thought it was.

We are now able to connect to the VIP address on the port specified in SSAS and it appears to connect OK (I can connect from the front-end web server using SQL Management Studio so I'm assuming its working)

However, the KB article you posted has got me thinking that maybe we need to configure an application name for it to work - I'll need to speak to the DBA's because I'm out of my depth with this already - I'm just an IIS guy ;-)

Thanks again.

Paul