Large I/Os are split into 64 KB units when using LSILogic Driver

Products

• VMware vSphere ESXi

Issue/Introduction

In Windows XP virtual machines using the LSILogic driver, I/Os of a size larger than 64 KB may be split into multiple I/Os of a maximum size of 64 KB. This might adversely affect I/O performance.

Environment

VMware ESX 4.1.x
VMware ESXi 4.0.x Installable
VMware ESXi 4.1.x Installable
VMware ESXi 4.0.x Embedded
VMware ESX Server 2.5.x
VMware vSphere ESXi 5.0
VMware ESX 4.0.x
VMware ESXi 3.5.x Installable
VMware ESX Server 3.5.x
VMware ESXi 3.5.x Embedded
VMware ESXi 4.1.x Embedded
VMware ESX Server 3.0.x

Resolution

You may be able to improve I/O performance by editing the registry entry

HKLM\SYSTEM\CurrentControlSet\Services\Symmpi\Parameters\Device\MaximumSGList



Refer to the section 2.2.6.1 Large Block Size Support in the LSI Fusion-MPT Device Management User's Guide

Note: The preceding link was correct as of November 5, 2014. If you find the link is broken, provide feedback and a VMware employee will update the link.

For more information see Guest Operating System Storage Considerations in the Performance Best Practices for VMware vSphere 5.0.