[Fedora-directory-users] Replication Possibilities

[Paxton, Darren]

Hi again all,

Managed to get myself to a  pretty good place with my configuration, but
would appreciate another pointer from yourselves.

Currently I have the system up and running with two servers (master1 and
master2) in a 2-way multi-master replication mode.

Master1 also has a Windows Synchronisation Agreement with adserver1,
which is also working, however it is working in a two-way mode,
propagating changes made on the Fedora Directory back to Active
Directory.

Unfortunately, our current strategy is to have Active Directory as the
single Directory for user management so as to make our Service Desk more
efficient. We also have a policy of removing all single points of
failure from within our enterprise, therefore I was looking at having
two windows sync agreements from two Fedora Master servers to two
different members of the same Active Directory.

The two Fedora Servers would also obviously need to be in sync (hence
the multi-master setup) but probably with a number of read-only consumer
servers dotted around the globe.

The question, therefore, is what would be the best way in terms of
replication design, to achieve this objective?

Basically, I want to achieve the following:

AD2 -> FD2 <-> FD1 <- AD1
            / |              |\
          /   |              |  \         
        V   V             V  V
    FD3   FD4     FD5  FD6

Thanks in advance for any assistance you can provde.

Cheers

Darren

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[David Boreham]

Paxton, Darren wrote:
> Unfortunately, our current strategy is to have Active Directory as the 
> single Directory for user management so as to make our Service Desk 
> more efficient. We also have a policy of removing all single points of 
> failure from within our enterprise, therefore I was looking at having 
> two windows sync agreements from two Fedora Master servers to two 
> different members of the same Active Directory.

You can configure this setup, but I don't think it'll quite work.
Bad things such as loops between the AD replication and
FDS replication can occur. Ulf Weltman did some investigation
on this a while back. You might be able to find his comments
in the list archive.

[Ulf Weltman]

David Boreham wrote:
> Paxton, Darren wrote:
> > Unfortunately, our current strategy is to have Active Directory as 
> > the single Directory for user management so as to make our Service 
> > Desk more efficient. We also have a policy of removing all single 
> > points of failure from within our enterprise, therefore I was looking 
> > at having two windows sync agreements from two Fedora Master servers 
> > to two different members of the same Active Directory.
>
> You can configure this setup, but I don't think it'll quite work.
> Bad things such as loops between the AD replication and
> FDS replication can occur. Ulf Weltman did some investigation
> on this a while back. You might be able to find his comments
> in the list archive.

This is the configuration I debugged:  In a configuration with two DS in 
MMR (M1 and M2) and two AD in the same domain (AD1 and AD2), M1 is 
configured to sync with AD1 and M2 to sync with AD2, and password sync 
on AD1 pointing to M1 and on AD2 pointing to M2, we have a ring 
configuration with good availability.

From what I hear it went into use with a couple of limitations:
Dual winsync paths results in LDAP ADD collision on AD 
(https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=182515)
Dual winsync paths results in LDAP DEL collision on DS 
(https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=184155)

[Edward Capriolo]

I can not give an authoritative answer, but if your active directory is 2003
server your active directory itself is multimaster ( no more PDC and SDC ).
It seems theorically possible to install active directory sync on both nodes
but leave it running only on one domain controller. Something like this:

AD2 <-> AD1
        |
LoadBalancer
        |
FD2 <->FD1

Here are some maybes. The configuration of the winsync agreements might have
issues communicating with a proxy or load balanced LDAP server. Also I do
not know of any HA product that would be able to fail winsync on a windows
server.

On 3/19/07, Paxton, Darren  wrote:
> Hi again all,
>
> Managed to get myself to a  pretty good place with my configuration, but
> would appreciate another pointer from yourselves.
>
> Currently I have the system up and running with two servers (master1 and
> master2) in a 2-way multi-master replication mode.
>
> Master1 also has a Windows Synchronisation Agreement with adserver1, which
> is also working, however it is working in a two-way mode, propagating
> changes made on the Fedora Directory back to Active Directory.
>
> Unfortunately, our current strategy is to have Active Directory as the
> single Directory for user management so as to make our Service Desk more
> efficient. We also have a policy of removing all single points of failure
> from within our enterprise, therefore I was looking at having two windows
> sync agreements from two Fedora Master servers to two different members of
> the same Active Directory.
>
> The two Fedora Servers would also obviously need to be in sync (hence the
> multi-master setup) but probably with a number of read-only consumer servers
> dotted around the globe.
>
> The question, therefore, is what would be the best way in terms of
> replication design, to achieve this objective?
>
> Basically, I want to achieve the following:
>
> AD2 -> FD2 <-> FD1 <- AD1
>             / |              |\
>           /   |              |  \
>         V   V             V  V
>     FD3   FD4     FD5  FD6
>
> Thanks in advance for any assistance you can provde.
>
> Cheers
>
> Darren
>
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> using any information contained herein. Please inform us of the erroneous
> delivery by return e-mail. Thank you for your co-operation.
>
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> the Financial Services Authority. Registered in England No. 984275.
> Registered Office: 1 Tower Place West, Tower Place, London, EC3R 5BU.
>
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[David Boreham]

Eddie C wrote:
> I can not give an authoritative answer, but if your active directory 
> is 2003 server your active directory itself is multimaster ( no more 
> PDC and SDC ). It seems theorically possible to install active 
> directory sync on both nodes but leave it running only on one domain 
> controller. Something like this:
>
> AD2 <-> AD1
>         |
> LoadBalancer 
>         |
> FD2 <->FD1

This is a cool idea, but it may not work because FDS uses the
AD sync control to perform incremental inbound updates.
It's quite likely that the two AD servers would have different
states for the sync cookie. You could work around this
by initiating a full sync when failing over between ADs.

[Paxton, Darren]

On Mon, 2007-03-19 at 08:11 -0600, David Boreham wrote:

Eddie C wrote:
    
    > I can not give an authoritative answer, but if your active
directory 
    > is 2003 server your active directory itself is multimaster (
no more 
    > PDC and SDC ). It seems theorically possible to install active
> directory sync on both nodes but leave it running only on one domain

> controller. Something like this:
    >  
    >  
    > AD2 <-> AD1
    >         |
    > LoadBalancer 
    >         |
    > FD2 <->FD1
    >  
    
    This is a cool idea, but it may not work because FDS uses the
    AD sync control to perform incremental inbound updates.
    It's quite likely that the two AD servers would have different
    states for the sync cookie. You could work around this
    by initiating a full sync when failing over between ADs.

THanks for the comments so far, it appears that if I can mitigate the
risk, then I can just leave a single agreement in place between FDS and
AD.

The other question though, regarding one-way from AD to FDS - anyone got
any thoughts on that?

Cheers

Darren 
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recipient, you should destroy the email message and any attachments or
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or using any information contained herein. Please inform us of the
erroneous delivery by return e-mail. Thank you for your co-operation.

Mercer Human Resource Consulting Limited is authorised and regulated by
the Financial Services Authority. Registered in England No. 984275.
Registered Office: 1 Tower Place West, Tower Place, London, EC3R 5BU.

[David Boreham]

Paxton, Darren wrote:
> The other question though, regarding one-way from AD to FDS - anyone 
> got any thoughts on that?

The sync code wasn't designed to allow this. However
there are a couple of things you could consider :
1. configure FDS access control to disallow modifications
on attributes that are sync'ed to AD. If there are no
pretinent modifications then nothing will get sync'ed to AD.
2. Hack the code to turn off the FDS->AD (outbound)
change propagation.