VNXe: What should be the value for parameter reclaim-unit=number in VNXe? (DELL EMC User correctable)

           

   Article Number:     503006                                   Article Version: 4     Article Type:    Break Fix 
   

 


Product:

 

VNXe2 Series

 

Issue:

 

 

   

      To reclaim unused storage blocks on a VMFS datastore for a thin-provisioned device, we need to run the below command from Vmware   
   
      esxcli storage vmfs unmap --volume-label=volume_label|--volume-uuid=volume_uuid --reclaim-unit=number   
   
     
      Parameter description is as below:   
   
     
      -l|--volume-label=volume_label     
      The label of the VMFS volume to UNMAP. This is a mandatory argument. If you specify this argument, do not use -u|--volume-     
      uuid=volume_uuid.   
        
      -u|--volume-uuid=volume_uuid     
      The UUID of the VMFS volume to UNMAP. This is a mandatory argument. If you specify this argument, do not use -l|--volume-label=volume_label.   
        
      -n|--reclaim-unit=number     
      The number of VMFS blocks to UNMAP per iteration.   
        
      What should be the value for --reclaim-unit=number in VNXe?   
                                                                

 

 

Resolution:

 

 

   

      The reclaim-unit=number is an optional argument and if not specified, the command uses a default value of 200.     
      The default value of 200 for the -n number or --reclaim-unit=number argument is appropriate in most environments, but some array vendors may suggest a larger or smaller value depending on how the array handles the SCSI UNMAP command.     
     
      The reclaim-unit=number is specified as per below configuration statistics:     
          
   
      200 MB for 1 MB block VMFS3 / VMFS5       
        800 MB for 4 MB block VMFS3       
        1600 MB for 8 MB block VMFS3
   
   
     
     
      VNXe supports VMFS5 format with 1 MB of block size, hence 200 which is the default VMFS blocks to UNMAP is appropriate for VNXe environments.     
     
      Hence, you may leave the argument "reclaim-unit=number" as it is, it will by default will take 200 value.   
                                                             

 

 

Notes:

 

 

   
    The associated VMware kb is:   
    https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2057513