Recommended Windows iSCSI initiator Registry configuration

Note: The VPSA Connect script automatically set the registry settings appropriately. This article is needed only if the automatic connection script has not run.

The following iSCSI registry settings (in hex) are recommended for Windows Hosts connected to a VPSA:

 

Location:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E97B-E325-11CE-BFC1-08002BE10318}\0001\Parameters]

 

1. MaxRequestHoldTime

Maximum time (in seconds) for which requests will be queued if connection to the target is lost and the connection is being retried. After this hold period, requests will be failed with "error no device" and device (disk) will be removed from the system

"MaxRequestHoldTime"=dword:00000078

 

2. LinkDownTime

This value determines how long requests will be held in the device queue and retried if the connection to the target is lost. If MPIO is installed this value is used. If MPIO is not installed MaxRequestHoldTime is used instead.

"LinkDownTime"=dword:00000078

 

3. SRBTimeoutDelta

The timeout set by class drivers (such as disk.sys, etc) for various requests does not take into account network delays. This value is used to increment the timeout set by class drivers.

SrbTimeoutDelta can be as low as 5 seconds. If it is lower than that, initiator will use 15 instead.

SrbTimeoutDelta gets added to the timeout set by the class driver

"SrbTimeoutDelta"=dword:00000078

 

4. WMIRequestTimeout

Timeout value set for WMI requests such as LoginToTarget, LogoutFromTarget, SendTargets, etc.

“WMIRequestTimeout”=dword:0000000F

 

5. The below values should be set to the maximal IO size that you expect to issue. The example demonstrates values suitable for 256Kb IO size (256Kb == 0x40000 bytes)

"MaxTransferLength"=dword:00040000
"MaxBurstLength"=dword:00040000
"FirstBurstLength"=dword:00040000
"MaxRecvDataSegmentLength"=dword:00040000

 

6. In addition, make sure the following values are set properly (these are the defaults):

"InitialR2T"=dword:00000000
"ImmediateData"=dword:00000001

 

After setting the registry values, it is best to reboot the machine. If it is needed to avoid reboot, then:
  • Logout from all iSCSI sessions
  • Go to "Server Manager" => "Diagnostics" => "Device Manager" => "Storage Controllers" => "Miscrosoft iSCSI Initiator"
  • Right-click on it and select "Disable". Wait until operation completes
  • Right-click on it again and select "Enable". Wait until operation completes.

Note:
You may you use the following Power Shell script to automatically adjust the parameters above (1-4). 

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