Dell EMC Metro node 7.1 Administrator Guide

Enabling/disabling WriteSame (16)

VMware servers discover whether the WriteSame (16) SCSI command is supported:

• During initial storage scanning
• When the DataMover.HardwareAcceleratedInit value on the ESX host is enabled (or toggled if it is enabled)

Virtual Machine operations may experience significant performance degradation if WriteSame (16) is not enabled.

Metro node allows WriteSame (16) to be enabled/disabled for all storage associated with metro node, using a single command. When WriteSame (16) is disabled on metro node, storage volumes, do not include WriteSame (16) support information in their responses to inquiries from hosts.

Support for WriteSame (16) can be enabled or disabled at two levels:

• Storage view - Enabled or disabled for all existing storage views. A storage view created after WriteSame (16) is enabled/disabled at the storage view level inherits the system default setting. Dell EMC recommends maintaining uniform WriteSame (16) setting on all storage views in metro node.

  If WriteSame (16) must be disabled for a given storage view, it must be disabled on all existing and future storage views. To make future storage views to reflect the new setting, change the system default.

• System default - Enabled or disabled as a system default. A storage view created after WriteSame (16) is enabled/disabled at the system default level inherits the system default setting. If the system default is enabled, WriteSame (16) support for the new storage view is also enabled.
  CAUTION:To disable the Write Same 16 default template, you must disable Write Same 16 for all existing views, and disable Write Same 16 template so that all future views will be Write Same 16 disabled. 
To enable the Write Same 16 default template, you must enable Write Same 16 for all existing views, and enable Write Same 16 template so that all future views will be Write Same 16 enabled.