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1. Summary

1.1. Overview

The CMM is a new layer in the MDS which cares about all clustered metadata issues and relationships. The CMM does the following:

  • Acts as layer between the MDT and MDD.

  • Provides MDS-MDS interaction.

  • Queries and updates FLD.

  • Does the local or remote operation if needed.

  • Will do rollback - epoch control, undo logging.

2. CMM functionality

CMM chooses all servers involved in operation and sends depended request if needed. The calling of remote MDS is a new feature related to the CMD. CMM mantain the list of MDC to connect with all other MDS.

3. Objects

The CMM can allocate two types of object - local and remote. Remote object can occur during metadata operations with more than one object involved. Such operation is called as cross-ref operation.

4. Code

lustre/cmm