Changing Paravirtualized SCSI Controller Device Queue Depth in VMware ESXi 4.x and later

Products

• VMware vSphere ESXi

Issue/Introduction

This article provides steps to change the disk queue depth for a Paravirtualized SCSI adapter on Windows.

You may need to increase the disk queue depth for a Paravirtualized SCSI adapter to improve performance due to heavy disk workload.

Environment

VMware vSphere ESXi 5.0
VMware ESX 4.0.x
VMware ESXi 4.1.x Embedded
VMware ESXi 4.0.x Embedded
VMware ESXi 4.1.x Installable
VMware ESXi 4.0.x Installable
VMware ESX 4.1.x

Resolution

To change the queue depth for disks attached to a Paravirtualized SCSI adapter:

Note: This procedure modifies the Windows registry. Before making any registry modifications, ensure that you have a current and valid backup of the registry and the virtual machine. For more information on backing up and restoring the registry, see the Microsoft article 136393.

1. Click Start > Run, type regedit, and press Enter. The Registry Editor window opens.
2. Navigate to this path:
   
   [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\pvscsi\Parameters\Device]
   
   Note: If the end of the path does not exist, create the last keys.
   
   
3. In the Device key, create or modify a string value named DriverParameter.
4. Set the value data of the DriverParameter to:
   
   "MaxQueueDepth=128"
   
   Note: Do not remove the quotation marks.
   
   
5. Reboot the guest operating system.

Additional Information

ESX LUN Queue Depth (which by default is 30 on Emulex and 32 on QLogic) must be changed if you want to go beyond 64 with the PVSCSI driver. For more information, see Changing the queue depth for QLogic and Emulex HBAs (1267).

Notes:

• In some scenarios you may need to make changes on the storage as it has similar limitations on I/O per LUN at a time.
• The per device queue depth can still be limited by the SCSI adapter queue depth, which is 256 by default for the PVSCSI adapter. For more information on increasing the adapter queue depth in addition to the disk queue depth, see Large-scale workloads with intensive I/O patterns might require queue depths significantly greater than PVSCSI default values (2053145).
  
  

Note: The links in this article were correct as of November 5, 2013. If you find a link is broken, provide feedback and a VMware employee will update the link.Large-scale workloads with intensive I/O patterns might require queue depths significantly greater than Paravirtual SCSI default values