Windows iSCSI configuration requirements are split into two types. These requirements are needed on both staging and target servers. 

  1. iSCSI configuration required for operational stability.
  2. Optional iSCSI parameters for performance improvement.
When target environments are discovered, Delphix will configure the Microsoft iSCSI Initiator Service for Automatic startup.

iSCSI Configuration Required for Operational Stability

The following Microsoft iSCSI Initiator configuration parameters are required for the target and staging Hosts. For details about configuring registry settings, see How to Modify the Windows Registry.

You must reboot the Windows server reboot after changing the iSCSI configuration parameters.

Registry KeyRegistry ValueTypeData
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\iSCSI\DiscoveryMaxRequestHoldTimeREG_DWORD0x384 (900)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DiskTimeOutValueREG_DWORD0x384 (900)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E97B-E325-11CE-BFC1-08002BE10318}\<Instance Number>\Parameters

MaxRequestHoldTimeREG_DWORD0x12C (300)

These settings will improve operational stability for VDBs and staging databases. If these settings are not adjusted, SQL Server may raise errors if VDBs are accessed during a temporary infrastructure outage. Affected VDBs may need to be manually restarted using the Continuous Data Engine. 

Delphix Knowledge Base article KB1251 includes scripts to validate or set registry parameters so that they meet current Delphix recommendations.

Optional iSCSI Parameters for Performance Improvement

The following iSCSI Registry setting may improve SQL Server dSource and VDB performance on the staging and target hosts.

Registry KeyRegistry ValueTypeData

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\<Interface GUID>

TcpAckFrequencyREG_DWORD0x1 (1)

This setting is recommended for storage networks in Microsoft's TechNet article iSCSI and the Nagle Algorithm, and described in Microsoft's document TcpAckFrequency to control the TCP ACK behavior.

In some environments, adjusting this setting may not improve performance compared to the Windows defaults. Modifications to this registry parameter should be tested in each environment, to confirm that this provides a performance improvement.

Identifying the Instance Number for iSCSI Control Class Initiator Drivers 

  1. From the Windows toolbar, click Start and select Run from the menu. 
  2. Type regedit in the Open field and click OK.
  3. Go to the following registry key:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E97B-E325-11CE-BFC1-08002BE10318}\<Instance Number> where the value of <Instance Number> is the one that shows a DriverDesc value of Microsoft iSCSI InitiatorUnder the registry key, locate and expand the plus (+) sign next to instance number. In this example below the value of instance number is 0002. 

 Value of Instance Number

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