one interesting question about ntds.dit

[John]

one interesting question:

We have 3 domain controllers in W2K environment. I just check the
file ntds.dit size and notice that each domain controller has different
size of ntds.dit. If there is no replication error, should the size of
ntds.dit be the same on three DCs?

Thanks for the help,

John

[Herb Martin]

Post by John
We have 3 domain controllers in W2K environment. I just check the
file ntds.dit size and notice that each domain controller has different
size of ntds.dit. If there is no replication error, should the size of
ntds.dit be the same on three DCs?

Nope. There are several reasons the sizes will vary,
starting with the fact that the files aren't replicate, but
rather the data records within the files.

First cause of differences is the case where one of
the servers has been around longer and gone through
test periods where records were added/deleted in
bulk (the default is to never reclaim such available
space BACK to the OS -- i.e., the file size is never
reduced without manual intervention.

When a new DCPromo is performed only the live
records are replicated.

Second big difference will be if one is a GC (especially
in a large forest) and the others are not.

Now, for a small, default domain they should be roughly
the same, staying at the default 10 MB size.

[Neil Ruston]

In addition, why not consider an offline defrag on all DCs. The most likely
reason for dit file differences, is due to fragmentation (as alluded to by
Herb).

An offline defrag will remove any whitespace from the dit file.

These articles explains how to measure whitespace and how to offline defrag
http://www.microsoft.com/technet/prodtechnol/windowsserver2003/library/TechRef/54094485-71f6-4be8-8ebf-faa45bc5db4c.mspx

http://support.microsoft.com/?kbid=232122

neil

Post by Herb Martin

Post by John
We have 3 domain controllers in W2K environment. I just check the
file ntds.dit size and notice that each domain controller has different
size of ntds.dit. If there is no replication error, should the size of
ntds.dit be the same on three DCs?

Nope. There are several reasons the sizes will vary,
starting with the fact that the files aren't replicate, but
rather the data records within the files.
First cause of differences is the case where one of
the servers has been around longer and gone through
test periods where records were added/deleted in
bulk (the default is to never reclaim such available
space BACK to the OS -- i.e., the file size is never
reduced without manual intervention.
When a new DCPromo is performed only the live
records are replicated.
Second big difference will be if one is a GC (especially
in a large forest) and the others are not.
Now, for a small, default domain they should be roughly
the same, staying at the default 10 MB size.
--
Herb Martin, MCSE, MVP
Accelerated MCSE
http://www.LearnQuick.Com
[phone number on web site]

[Herb Martin]

Post by Neil Ruston
In addition, why not consider an offline defrag on all DCs. The most likely
reason for dit file differences, is due to fragmentation (as alluded to by
Herb).
An offline defrag will remove any whitespace from the dit file.

The main reason would be that offline defrag is seldom
needed nor advantageous significantly.

It's overdocumented for something seldom worth doing.
--
Herb Martin, MCSE, MVP
Accelerated MCSE
http://www.LearnQuick.Com
[phone number on web site]

Post by Neil Ruston
These articles explains how to measure whitespace and how to offline
defrag.
http://www.microsoft.com/technet/prodtechnol/windowsserver2003/library/TechRef/54094485-71f6-4be8-8ebf-faa45bc5db4c.mspx
http://support.microsoft.com/?kbid=232122
neil

Post by Herb Martin

Post by John
We have 3 domain controllers in W2K environment. I just check the
file ntds.dit size and notice that each domain controller has different
size of ntds.dit. If there is no replication error, should the size of
ntds.dit be the same on three DCs?

Nope. There are several reasons the sizes will vary,
starting with the fact that the files aren't replicate, but
rather the data records within the files.
First cause of differences is the case where one of
the servers has been around longer and gone through
test periods where records were added/deleted in
bulk (the default is to never reclaim such available
space BACK to the OS -- i.e., the file size is never
reduced without manual intervention.
When a new DCPromo is performed only the live
records are replicated.
Second big difference will be if one is a GC (especially
in a large forest) and the others are not.
Now, for a small, default domain they should be roughly
the same, staying at the default 10 MB size.
--
Herb Martin, MCSE, MVP
Accelerated MCSE
http://www.LearnQuick.Com
[phone number on web site]

[Neil Ruston]

I agree Herb, but was offering a suggestion in regard to the post. If the
poster is concerned that he has dit file differences, then an offline defrag
should help resolve that 'issue'.

I certainly wouldn't advocate that this be done regularly, but if the poster
has space issues or concerns, then this is one approach well worth
considering.

neil

Post by Herb Martin

Post by Neil Ruston
In addition, why not consider an offline defrag on all DCs. The most likely
reason for dit file differences, is due to fragmentation (as alluded to by
Herb).
An offline defrag will remove any whitespace from the dit file.

The main reason would be that offline defrag is seldom
needed nor advantageous significantly.
It's overdocumented for something seldom worth doing.
--
Herb Martin, MCSE, MVP
Accelerated MCSE
http://www.LearnQuick.Com
[phone number on web site]

Post by Neil Ruston
These articles explains how to measure whitespace and how to offline
defrag.
http://www.microsoft.com/technet/prodtechnol/windowsserver2003/library/TechRef/54094485-71f6-4be8-8ebf-faa45bc5db4c.mspx
http://support.microsoft.com/?kbid=232122
neil

Post by Herb Martin

Post by John
We have 3 domain controllers in W2K environment. I just check the
file ntds.dit size and notice that each domain controller has different
size of ntds.dit. If there is no replication error, should the size of
ntds.dit be the same on three DCs?

Nope. There are several reasons the sizes will vary,
starting with the fact that the files aren't replicate, but
rather the data records within the files.
First cause of differences is the case where one of
the servers has been around longer and gone through
test periods where records were added/deleted in
bulk (the default is to never reclaim such available
space BACK to the OS -- i.e., the file size is never
reduced without manual intervention.
When a new DCPromo is performed only the live
records are replicated.
Second big difference will be if one is a GC (especially
in a large forest) and the others are not.
Now, for a small, default domain they should be roughly
the same, staying at the default 10 MB size.
--
Herb Martin, MCSE, MVP
Accelerated MCSE
http://www.LearnQuick.Com
[phone number on web site]

[Abdelilah Nejjari]

I noticed exactly the same thing with DCs in differents sites. There is
no replication errors.

When checked, it seems that the GC role get the dit file bigger.