Introduction
VMDirectPath I/O allows a guest operating system on a virtual machine to directly access physical PCI and PCIe devices connected to a host. Each virtual machine can be connected to up to two PCI devices. PCI devices connected to a host can be marked as available for passthrough from the Hardware Advanced Settings in the Configuration tab for the host.
VMDirectPath allows guest operating systems to directly access an I/O device, bypassing the virtualization layer. This direct path, or passthrough can improve performance for VMware ESXTM systems that utilize high‐speed I/O devices, such as 10 Gigabit Ethernet.
VMware unveils VMDirectPath technology, Intel to support it with Nehalem:
http://www.dabcc.com/article.aspx?id=8474
http://www.virtualization.info/2008/08/vmware-unveils-vmdirectpath-technology.html
Intel releases new CPUs and NICs with nested page tables and I/O virtualization:
http://www.virtualization.info/2009/03/intel-releases-new-cpus-and-nics-with.html
Configuration
Configuring VMDirectPath I/O pass-through devices on an ESX host -
http://kb.vmware.com/kb/1010789
Configuration Examples and Troubleshooting for VMDirectPath -
http://www.vmware.com/pdf/vsp_4_vmdirectpath_host.pdf
Configuration Examples and Troubleshooting for VMDirectPath
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http://www.youtube.com/watch?v=WhMkmTqBbUA{youtube}
Configuring VMDirectPath IO with Cisco UCS and vSphere
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http://www.youtube.com/watch?v=jmQ5Ej8r-aA{youtube}
Requirements
- vSphere (well… common)
- Intel Virtualization Technology for Directed I/O (VT-d)
- AMD IP Virtualization Technology (IOMMU)
- Devices must be connected to the host and marked available for pass through
- VMs require hardware version 7
VMDirectPath I/O is experimentally supported for the following Storage and Network I/O devices:
- QLogic QLA25xx 8 Gb Fibre Channel adapters
- Emulex LPe12000 8 Gb Fibre Channel adapters
- LSI 3442e-R and 3801e (1068 chip based) 3 Gb SAS adapters
- Intel 82598 10 Gigabit Ethernet controller
- Broadcom 57710 and 57711 10 Gigabit Ethernet controllers
VMware regularly adds support for new hardware. Check on HLC:
http://www.vmware.com/resources/compatibility/search.php
Limitations
When using VMDirectPath you lose following features:
- VMotion
- Storage VMotion
- FT
- Device hot add
- Suspend and resume
- Record and replay
USB virtualization
If your server has support for device pass-through you may be able to provide USB access to Virtual Machines:
Enable USB Support for ESXi with VMDirectPath -
http://vm-help.com/esx40i/VMDirectPath/USB_Setup.php
VMware ESXi4 and VMDirectPath -
http://www.petri.co.il/vmware-esxi4-vmdirectpath.htm
Note that you give (if it works...) the entire USB chipset... so all the USB devices to a single VM!
Sources
Introduction from SimonLong Blog
http://www.simonlong.co.uk/blog/2009/08/03/vmware-vmdirectpath-io/
VMDirectPath? Paravirtual SCSI? – vSphere VM Options and You!
http://professionalvmware.com/2009/08/vmdirectpath-paravirtual-scsi-vsphere-vm-options-and-you/