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Is PVSCSI Ready for Mainstream Workloads?

Wednesday, July 13 2011 13:00 Written by Mattias Sundling

VMware Paravirtualized SCSI (PVSCSI) introduced in vSphere was a special purposed driver for high-performance storage adapters that offered greater throughput and lower CPU utilization for virtual machines. According to tests PVSCSI offers 12% improvement in throughput and 18% less CPU cost compared to LSI SCSI.

In the early releases it had lots of limitations:

• FT not supported
• PVSCSI on boot disk not supported
• Hot Add not supported
• Only suited for heavy disk IO demanding workloads due to how PVSCSI handles interrupt coalescing
• Very limited OS support
• Not for Direct Attached Storage

All of these limitations are gone now (vSphere 4.1) except the two last bullets.

Lots of benefits:

• Simplicity, only having one template to maintain
• Don´t have to worry about changing virtual hw/driver if VM is starting to require higher disk IO at a later state
• Allows you to run more VMs -> higher VM density
• Increased disk IO performance

I wouldn´t change to PVSCSI on existing VMs if there is not a demand for high disk IO. But I would like to see more adoption of PVSCSI going forward as most people are basing their decisions on old and inaccurate information.

Please leave some comments on your experiences on PVSCSI (good and bad).

For more info:

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1017652

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1010398

http://www.vmware.com/pdf/vsp_4_pvscsi_perf.pdf

/Mattias

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