What’s the deal with the new PVSCSI drivers?

New in vSphere are ParaVirtualized SCSI drivers.  From what I have read at various places, 12% performance throughput increase with 18% decrease on guest CPU loads!  Sounds great – What’s the catch?

Seems the new PVSCSI drivers are not supported for boot drives on the VMs (Chalk up one more reason to NOT have just a C drive).  The situations I am running into are that many clients HAVE already moved to a single drive server model.  Many of the environments I am running into have settled on a server standard consisting of a 25 – 40 GB C drive for both OS and data.  For most of the infrastructure servers, this model seems to have worked out nicely.  Run out of room?; just grow those puppies without breaking a sweat!  Performance on these grossly underutilized servers does not seem to be a factor.  A nice balance of performance vs. manageability.

At first glance, I figured I would be rolling out just about every VM with these new PVSCSI drivers, now, I think it will probably be the exception.  PVSCSI will be a potential tool in my belt to help solve VM performance issues when the LSI is not up to the job.  I think some of the selection criteria for when I will use PVSCSI will be server’s with applications that naturally lends itself to a multiple drive partition layout (think Mail and Database applications) in which adding PVSCSI drivers to the second, third and remaining drives will be a no brainer.  For the vast majority of my VMs though, chugging happily along at 10% utilization, the LSI Logic Parallel driver will probably fit the bill.

How bout You?  🙂