Forum Discussion
Carl_Brothers
Employee
EmployeeLTM versus SAP message server for BW
I had set up a VS in the LTM for a SAP BW reporting module on a set of servers, which seemed to work fine applying the same rules layed out in the Netweaver SOA deployment guide. Now the BW module is included in the main internal SAP netweaver portal site via frames on the web page.
The SAP admins moved away from the previously constructed VS in the F5 citing that message server would always make a better initial load balancing decision. Now I would tend to think that putting soo much credibility on the initial LB decision is shaky ground to stand on as the performance of the node you connect to can degrade while connected, regardless of solution. The director of the SAP admin group is adamant about having this degree of functionality in the LTM or the use of the LTM is a non-starter. Use of logic like your CPU cycles are more valuable than the CPU cycles in my 6800 (BTW it averages less than 3% CPU used) has fallen on deaf ears thus far I feel.
So far I think the closest option would be the use of Dynamic Ratio LB and the use of SNMP DCA monitors. Anyone got a similar situation or set of challenges as well as a solution?
Thanks,
Carl B
3 Replies
John_Clowers_16Nimbostratus
CarlB -
I see the SAP application owners pushing the SAP Web Dispatcher all the time and have found that while it does integrate nicely into the SAP solution you do lose the ability to offer some key components that you have with external load balancing. Since Web Dispatcher requires the message server to update the status of the portal services you will always have some delay and possible persistence issues that will need to be addressed with a re-authentication in a failure state.
Using the LTM we can also check the health of the servers as you pointed out in your post, and with the version 10.x of TMOS you can now turn on inband monitoring. The LTM will provide a high availability environment, and with iRules and iControl you can modify the traffic to meet you customers needs and manage the LTM.- Carl_BrothersCan you expand on the V10 inband monitoring?
I don't have an issue with the web dspatcher debate, rather the message server when used with the BI modules.
Thanks,
Carl B - One of the questions I have from your original post is that ". . . message server would always make a better initial load balancing decision." Message server isn't making load balancing decisions, in the traditional sense. It's providing information about the health and capability of the systems behind it.
It's been my experience that today, BIGIP can do a better job determining the load balancing decision than message server can because BIGIP can 1) Consult Message Server 2) Consult(Probe) the actual DI instance and 3) make an SNMP call to determine CPU, then based on all this information, make a load balancing decision. If uptime and reliability is a concern (99.99 or ever 99% over higher) it seems that this would be preferable to get this type of composite picture.
This solution is achieved through and external monitor type and a small amount of coding is required. If you do a search in Google for "Monitoring the Message Server Using the Browser." You will see the specification for how to call your message server. Parsing its output is very easy, though, unfortunately it's not in an XML datatype today. (Sorry I can't provide the link, it's part of a frameset and will probably get mangled if I post it directly here).
-Nojan
