couple questions...

[Ricardo Kleemann]

Thanks Joseph.

Mysql supports multi-master replication, which means you can have 2 servers 
as master and slave... so in that sense a pair should be usable for load 
balancing.

The reason I have LVS director in both A and B is because with only one, I 
have a single point of failure. The alternative of having an LVS in front of 
both A and B also means I need another server, and it becomes a single point 
of failure.

So I thought, if it were possible to run an instance of LVS on BOTH the A/B 
servers, and just use it for load-balancing the 2 db servers (which are 
setup with multi-master replication), then I would not have a single point 
of failure. Basically 2 redundant DB servers, and 2 redundant app servers.

Just wondering if that would work...

----- Original Message ----- 
From: "Joseph Mack NA3T" <jmack at wm7d.net>
To: "LinuxVirtualServer.org users mailing list." 
<lvs-users at LinuxVirtualServer.org>
Sent: Friday, August 04, 2006 3:17 PM
Subject: Re: couple questions...


> On Fri, 4 Aug 2006, Ricardo Kleemann wrote:
>
>> I'm horrible with ascii art... :-(
>
> No,no, it's beautiful (the bold lines, the striking constrast, the 
> original two fold symmetry...)
>
>> I guess we can look at it as a mini cluster with 4 servers. Servers A and 
>> B are application servers. Servers X and Y are database servers.
>>
>>
>>                   A
>>               (LVS)
>>                   |
>>              --------
>>              |      |
>>              X ---- Y
>>              |      |
>>              --------
>>                   |
>>               (LVS)
>>                   B
>>
>> X and Y are redundant, replicated database servers. Both A and B would 
>> have their database connections load-balanced between X and Y.
>>
>> So I was wondering if simply running LVS on BOTH server A and B, in order 
>> to achieve the load balancing, is feasible.
>>
>> In this case, the LVS is really directing local connections (on A or B) 
>> to the X/Y servers. It is not directing external connections from the 
>> internet.
>
> OK. Now I don't know why you're doing it, even after re-reading your 
> original post.
>
> Do you understand that you can't load balance database servers (X,Y in 
> your diagram), at least the ones like mysql, postgresql. If you don't, 
> read the section on database servers in the HOWTO. You can have one be a 
> failover backup for the other, but that's about it.
>
> I don't see why you have two LVS directors. The logical flow of 
> connections is no different to that with one director. It's like having 
> two routers, instead of one in front of X. If you want A and B to be a 
> failover pair then you need a common connection from them to the outside 
> world.
>
> Joe
>
> -- 
> Joseph Mack NA3T EME(B,D), FM05lw North Carolina
> jmack (at) wm7d (dot) net - azimuthal equidistant map
> generator at http://www.wm7d.net/azproj.shtml Homepage 
> http://www.austintek.com/ It's GNU/Linux!
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