OpenLDAP Cluster+Alteon

[Syahrul Sazli Shaharir <sazli@mimos.my>]

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Hi,

I am in a process of designing a highly-available LDAP service. The goals
of the design are (1) simple (2) scalable (3) redundant (4) Use existing
Alteon load balancers, which fan out connections to one IP to multiple
IPs.

The best I can think of so far:-

         LDAP clients
              |
        ______|______
       |___Alteon____|
        |     |     |
        |     |     |
        |     |     |
        o     o     o
      ldap1 ldap2 ldap3

ldap1, ldap2, ldap3 are multi-master OpenLDAP servers. Should be most
elegant, but AFAIK multi-master support in OpenLDAP is still experimental.

Single master with chaining is not available in OpenLDAP, so the only
alternative is single master with referrals:-

         LDAP clients
           |        |
        ___|________|___
       |_____Alteon_____|
         |   |    ||||
         |   |    ||||
         |   |    ||||
         o   o    oooo
        l1  l2    slaves

l2 is cold standby master, eg l1 and l2 maintains heartbeat, if l1 down,
l2 automatically wakes up and takes over, and vice versa. Both runs slurpd
and updates all the slaves as required. Not as pretty as I want [ Masters
not scalable, and LDAP clients need to handle write referrals correctly ],
but should work.

Ideas? Past experiences? TIA! :)

- --sazli
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