More on DFS Replication Limits

More on DFS Replication Limits

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A customer recently asked us to clarify the 1-TB DFS Replication limit described in an earlier post. Shobana Balakrishnan, our DFS Replication program manager, explains:

There are no architectural underpinnings of the 1TB limit – it is merely what we tested.  The Jet limits are much larger.  The theoretical limit comes from the number of files under a volume scope due to Jet limits and of course recovery times.  Theoretically the Jet DB can grow as large as 32 TB and assume ¼ used for ID records -> 8TB. Assuming an ID record is 1KB worst case, that is 8*10^9 files on the volume.

On a practical note, we have tested over 50 million files taking approx 1 TB of disk space. The database in this case was approx 20 GB.

I should also clarify bullet (5): A replication group can contain up to 256 members.

This is actually not a global replication group limit. A replication group can be arbitrarily large scaling to several thousands of members.  Each member must however only be connected to at most 256 partners - and actually this translates to bullet (3) where each server should have at most 128 partners (replicating in-and out). 



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  • very interesting... what is the default database location, and can it be moved?

  • I've asked Shobana to answer your question--here is her response:

    The database is secured (ACLed to SYSTEM) and located under the replicated folder volume’s System Volume Information.

    No, the database cannot be moved it resides on the same volume as the replicated folder root.  You can however rebalance your database size by moving replicated folders to a new volume by changing the replicated folder path. This will cause the old database entries to be tombstoned and deleted over time and new entries to be created in the DB on the new volume. DFSR will need to go through an initial sync which can be expedited by copying the files over to the new volume.  

  • [Updated on 10/5/06 to clarify areas where customers commonly have questions] The most frequent DFS Replication

  • Just to make sure I am not losing it:

    8*10^9 would make it 8 billion files.  Is it possible that the Jet database limit is 32GB (not TB), so the ID records occupy 8GB = 8*10^9B, which divided by the size of one record 10^3B, would give expected the 8*10^6= 8 million files?

    Two more questions:

    1. Where is the 1/4 allocation for ID records coming from?

    2. Is there a way to check how full is the Jet database?