[Users] High Availability Setup

Hi verybody, WARNING: Long e-mail..... I just started learning how to set up a "classical" configuration with load balancer, DB backend and so on....I was reading several threads of the mailing lists but since I am a begginer I would need some help and clarifications. Apologies if my questions have been solved before. [I read Greger and Granig (and more people, I guess) are working (?) on a document describing what I try to explain in the follofwing lines. I would like to know if you are on it or commercial strategies forced you to leave it...as it seems that HA setups are high confidential ;)] I'll try to draw what I have guessed from the threads and other literature... [SER1] [LB1] [SER2] . [DB (mysql cluster)] [LB2] . [SERn] LBi are the front-end load balancers. SER: do I have to say what are these?? (either openSER/SER. I will use the name SER for simplicity but I refer to both) DB: I placed mysql cluster because it seems to be the most common backend... Let me make an overview... Load Balancer For LB, it seems that dispacther module can be used. (I don´t remember who proposed to dispatch REGISTER with To: and INIVTE with Req-URI, why not using Call-ID?? For distributing the registration of a given user between several registrars?). Dispatcher module does not have failover in case SERi fails so somebody propose to use lcr. Using lcr module provides failover but does not guarantee to balance to the right instance of SER so I think the only option is to use dispatcher. Alternatives: Please correct me if I am wrong but there isn´t yet an LVR implementation being Call-ID aware.... DNS SRV records...lack of implementation in end-points and not NAT-friendly.. In order to provide high availability, I tried linux-ha between the 2 LBi for simplicity although it has some wasted resources. Is it worth to give a try to other IP failover aplications (anycast, quagga/bgp, vrrpd)? Anyone with more experience can comment their use?? SIP proxy SER....just a matter of taste what you want to use, SER or openSER.... I read about the cacheless usrloc patch but I could not find it on CVS...has it been integrated into the head branch??? has it been deprecated because of ...(please fill in the reason)? DB Backend For the DB backend...I am going to comment mysql clustering...I am using now 4.1.11 because it was already installed. Is it recommended to upgrade?? I tried setting the management node, a couple of data nodes, and I was trying to set a linux-ha configuration with ip take over for the mysql api node (is it possible??) but unsuccessfully: When the preferred mysql api node falls down, SER detects the connection is closed and all further requests are replied with "Internal Server Error" although the secondary mysql api has overtaken the service IP and ser database is properly populated. Is it possible to make SER reconnecting on mysql failure?? It reconnects to the preferred server once it comes back to live but it is impossible to connect to the secondary.... As you might have guessed I am a total begginer with mySQL... Thank for reading until this line, all kinds of comments are wellcome, Samuel.