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Wednesday, May 28, 2014

EMC ! EMC ! , Knowing about EMC Data Domain Filesystem

Hey all now a days there's lot of buzz about EMC i see lot of my customers switching to EMC , I have already started working on Data Domain and VNX i just wanted to share some of my experience and understanding.

The Data Domain file system resides on ddvar directory and it is like a root directory.  It can be shared as NFS/CIFS share but one cannot rename or delete it because it holds the operating environment binaries and configuration.

And you will have a Data Directory followed by sub-directory called collection 1 which will be like /data/col1 and by default there is only one collection i.e., collection #1 under col1 you will have folders or MTrees , the default is called backup where all your backups will be stored however you can create more Mtrees under /col1 and each Mtree can be managed individually it has its own permissions and quota settings ( If needed to restrict ). The maximum number of Mtrees is 100. Any Mtree can be mounted as NFS shares or Mapped as CIFS shares.

Also Quotas can be set on Mtrees where we have two types Hard and Soft quotas, Hard Quotas will restrict the users from writing any data once the limit is reached and Soft quota will send the warnings and alerts.

Each MTree can be individually managed with its own policies and permissions.  The max number of MTrees is 100, however after 14 there is a performance degradation in environments where there is a lot of read/write streams to each MTree.  Best practice dictates that you keep MTrees to 14 and to aggregate operations to one MTree where possible.  You can mount MTrees like any other CIFS/NFS share, however it is not recommended to mix protocol type.  VTL and DDBoost clients create their own MTree, as well.


  1. How many files can the filesystem handle? Can put tens or hundreds of millions of files on it?

  2. Probably EMC can store maximum of 256 Million