Data Domain: How to verify large object conversion status after DDOS or later version upgrade?[1]


   Article Number:     530025                                   Article Version: 3     Article Type:    How To 




Data Domain





    Datadomain Cloud Tier customers are moving long-term retention data from their data centers to the cloud in order to reduce their costs.  Cloud tier solution prior DD OS version is not highly optimized. It is generating a large number of small objects results in higher transaction costs for the customer.   
    In addition, private cloud providers have expressed concerns about the metadata overhead caused by a large number of small objects. Data Domain generates objects of size 64K on average and in some instances, the metadata used to represent an object is larger than the object itself.   
    In order to reduce the cost of tiering  and metadata overhead large object size (LOS) support is introduced in DD OS  and later version   

  1.         Data Domain system must be upgraded to DD OS or later version     
  3.         ECS must be running minimum version     
  5.         ECS usage will be inflated during Cloud GC due to copy forward phase. Hence it is recommended to ECS usable capacity under 70%.     
  7.         Multiple Cloud GC cycles will be required to convert current small objects to large object size     
    Allow system to complete first full cloud GC cycle   
    Review following information from daily autosupport reports for LOS conversion status after completing full cloud GC cycle   
    Cloud GC start and stop information    
    system.cloud_gc_start_date = 2018/11/28 08:40:34     
      system.cloud_gc_success_date = 2018/12/05 23:01:34
    Check GC stats information   
    GC stats for Physical Cleaning on ECS Success 2 Aborted 2     
      GC select phase details:                               Recent                 Cumulative     
      Number of pre-LOS L0 containers selected:              28277944               66822319  
    Highlighted number shows number of container written with small object size prior to DD OS or later upgrade     
    GC copy phase details:                                   Recent      Cumulative     
      Number of containers copied:                           13607971       23906868     
      L0 copy forward container and region stats:     
      Number of L0 containers copied:                        13362006       23371397     
      Number of pre-LOS L0 containers copied:                 8278682       18288073 
    Highlighted number shows number of container written with large object size during  this Cloud GC   
    Based on above information this system has (28277944-8278682) = 19999262 containers still pending for LOS conversion.   
    Following section of autosupport report shows commutative number of async request sent by Data Domain to ECS during this large object size conversion   
    CAL cloudunit-specific histogram for op latency with qdelay for small objects, unit: ECS, UUID: e5f628a176cd852b-755ce97d677xxxxx     
      op            mean      std-dev    <100 ms     <500ms   <1s        <5s       <10s       <30s       >30s      total        max        min     
      mc_async   6765.269ms   4401.129ms  0          170      91662   14206949   10135767    7926842     1108    32362498  533670.000    219.000