Data Domain destination system configured with MTREE replication may report higher usage if source system has fastcopy files in same MTREE

           

   Article Number:     539716                                   Article Version: 2     Article Type:    Break Fix 
   

 


Product:

 

Data Domain

 

Issue:

 

 

Data Domain destination system configured with MTREE replication may report higher usage if source system has fastcopy files in same MTREE                                                           

 

 

Cause:

 

 

By default fastcopy operation on Data domain file system(ddfs) does not set Base File tracking(BFT) flag.     
        
    During MTREE replication the fastcopied file will be replicated as a gen0 because during ingest fastcopy of the directory didn’t have the bft flag turned on. Also fastcopy files shares L0 segments with original file hence it does required additional space. Due to this it may show higher compression factor on source system compare to destination system   
   
    Example:  Information from sfs_dump from source and destination Data domain system   
        
    SRC fast copy file :   
        
    /data/col1/MTREE1/increment/backdata1: mtime: 1568680103968447000 fileid: 3751127 size: 5893005312 type: 9 seg_bytes: 5913233056 seg_count: 708373 redun_seg_count: 708373 (100%) pre_lc_size: 0 post_lc_size: 0 (0%) mode: 02000100640 start_offset: 0 end_offset: 18446744073709551615     
       
   
        
    DST:   
        
    /data/col1/MTREE1/increment/backdata1: mtime: 1568680103968447000 fileid: 3751127 size: 5893005312 type: 9 seg_bytes: 5912862460 seg_count: 708308 redun_seg_count: 704269 (99%) pre_lc_size: 41811242 post_lc_size: 27638454 (66%) mode: 02000100640 start_offset: 0 end_offset: 18446744073709551615   
        
        
    In above example since BFT is not set, hence it was replicated destination as gen0 file showing post_lc_size value.   
     
                                                           

 

 

Resolution:

 

 

 Turn on BFT for fastcopy using synthetic-optim option. Note this option is not documented   
        
    #filesys fastcopy source <src dir> destination <dst dir> synthetic-optim   
        
     Note this setting will be applied to newer fasctcopy files. It is not possible to reclaim data for data replicated without BFT.  Customer need to wait for fast-copy files to expire or manual clean-up is required