Re: OpenLdap DB size difference after slapcat and slapadd.

["matthew sporleder" <msporleder@gmail.com>]

On 7/5/06, Tech Guy <techguymenlo@yahoo.com> wrote:
> Hi,
>
> We recently ran into the OpenLDAP(v2.1.12) index
> corruption issue on a production system. I understand
> that there is a fix for this in later versions and we
> are in the process of upgrading our systems.
>
> My question was related to the back-end database size
> reduction we saw as a result of the steps we took to
> recover from the issue.
>
> Shutdown OpenLDAP
> Slapcat the database to an LDIF file
> SlapAdd'ed the database back.
>
> We noticed a reduction of size of ~200Mb and the ldbm
> directory changed from 1000Mb to 800Mb after the
> slapadd.
>
> Approximate distribution of size changes
> id2entry.dbb - Reduction of 163Mb
> dn2id.dbb    - Reduction of 54Mb
> index dbb    - Reduction of 11 Mb
>
> My only explanation was the database storage was
> fragmented before the slapcat and the slapadd resulted
> in an optimized storing of records.

Probably, LDBM doesn't do very aggressive checking.
Also, when entries are deleted from a berkeleydb environment, the
space is not necessarily all recovered.  Since slapcat/slapadd only
adds, I think having a size difference can be expected.

> Can someone explain the reduction in size? Also, is
> the slapcat and slapadd a recommended maintenance
> practice to improve performance in OpenLDAP?

If you can stomach the downtime, I don't think it hurts anything.