Several questions on Openldap for migration

[Francois Gnu <gnu699@gmail.com>]

Hello everybody,

First of all, sorry in advance for my approximate English.

I have several questions. Questions for which I did not find answer
until today, despite one very large number of reading of docs, faqs,
tickets etc. (I did not necessarily read everything, internet is so
vast).

Presentation:
I have to migrate all the servers of the company, from ubuntu
10.04.3lts (package openldap 2.4.21) to ubuntu 12.04lts (package
openldap 2.4.28).

Configuration:
Configuration of openldap, identical on all the servers (Masters and
Slaves), configuration of dynamic type (with cn=config ), with
reference ldap Masters in the config of slaves ; syncrepl (N-Way)
Multi-Master mode.
All servers are VMs on kvm.


Questions:
Questions according to several scenarios:
- there are problems of synchronization between 2 Masters, if the one
is in 2.4.21 and the other one in 2.4.28?
- there are problems of synchronization between 2 servers, if 1 Master
is in 2.4.21 and 1/severals Slave(s) in 2.4.28?
- there are problems of synchronization between 2 servers, if 1 Master
is in 2.4.28 and 1/several Slaves in 2.4.21?
- I want to do an update of part of the slaves servers. What it is
better to use?: acl or in syscrepl? Which is the most flexible?

MDB backend:
- can one use now the backend-mdb new in "production mode" with
openldap 2.4.28? Is it with good/enough stability? Or do I have to
stay with the backend-hdb and migrate towards backend-mdb later?
- Is it pisible to migrate from backend-hdb towards backend-mdb for
server in production, in the future?

Tcmalloc:
- I placed tcmalloc in this file '/etc/init.d/slapd' as this
"LD_PRELOAD=/usr/lib/libtcmalloc_minimal.so.0". Is it good? Is it the
good place/file?
- where can I find track of its load (of tcmalloc)? How can I see the
functioning of tcmalloc? In what file of log? The LSOF command no give
nothing.
- it is indicated in the site
"[URL="http://code.google.com/r/heybrowny-higmysql/source/browse/google-perftools-1.8.3/README?r=bf85e419619834120ab33c6358b6d16e833ee2ae&spec=svnadce3f5e52fd66eb901bb4e4287e28f7202a5599"]http://code.google.com/.../google-perftools-1.8.3/README[/URL]";
> "TCMALLOC_DEBUG=<level> -- the higher level, the more messages
malloc emits". It is indicated that more the number increase and more
tcmalloc verbose. But it is not indicated/informed has what
corresponds the numeros (levels) of log and until how much?
-to use "TCMALLOC_DEBUG", I have to use
"LD_PRELOAD=/usr/lib/libtcmalloc_minimal_debug.so.0" or keep
"LD_PRELOAD=/usr/lib/libtcmalloc_minimal.so.0"?

Backups and restore:
-the opinions diverge. Indeed, to make a backup/restore, slapadd
command is enough with the file created with slapcat? Or i need to
integrate (with slapadd) at first the config file (cn=config file) and
then the acl config file  and then the data of the users that were
created at the first installation of openldap 2.4.21?

So, I installed and configured openldap in 2005 on a debian for the
needs of a company but today many things changed and difficult to find
itself there.

Thank you in advance for taking time and your answers.


Francois
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Librement