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Re: The difference between the meta and ldap backends



> Hello all,
>
> I'm been working with OpenLDAP in a metadirectory configuration -- I'm
> using it to provide a merged view of two organization LDAP servers,
> along with a local database to support "external collaborators" (that
> is, people not otherwise affiliated with our organization).  In my
> limited testing it seems to be working reasonably well, but I'm not
> sure I completely understand all the components.  For example, I'm
> unsure of the difference between this:
>
>   database meta
>
>   uri ldap://serverA.example.com/ou=A,o=organization
>   uri ldap://serverB.example.com/ou=B,o=organization
>   # ...necessary suffix massaging...
>
>   database hdb
>   suffix o=organization
>
> And this:
>
>   database ldap
>   subordinate
>   suffix ou=A,o=organization
>   uri ldap://serverA.example.com
>   # ...rewriting...
>
>   database ldap
>   subordinate
>   suffix ou=B,o=organization
>   uri ldap://serverB.example.com
>   # ...rewriting...
>
>   database hdb
>   suffix o=organization
>
> Both seem to provide the same behavior; a search against
> o=organization will search all three directories.  Is either
> configuration preferable?  Is one backend considered more stable than
> the other?  is there some subtle difference in behavior that I'm
> missing?  I'd appreciate your input.

slapd-ldap(5) and slapd-meta(5) share some of the code.  slapd-ldap(5) is
usually few features ahead of slapd-meta(5).  In general, slapd-meta(5)
supports between 90 and 99% of the features of slapd-ldap(5).  The main
difference between the two setups you mentioned is in long searches that
span multiple targets.  Slapd-meta(5) operates in parallel, i.e. searches
are spawn simultaneously on all pertinent targets, and results are dealt
with as soon as they come in.  In a glued database layout, searches are
performed sequentially.  This has nearly no impact for local storage,
while it can have a significant impact in the case of proxied remote
targets.

p.

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