Vmware Scsi Lsi Logic Sas Driver

Retrofit a VM with the VMware Paravirtual SCSI Driver

Thanks. Worked good for me except for one adjustment I had to make. WIth VMware version 5.5, you don t get the option for SCSI 1:0 until you have used up all 15.

I wrote a blog article in Oct 2010 on this same topic that is still frequently referenced today so I figure it was due for an update.

So what should I choose as my vSCSI controller and what are the differences between them.

First, it s important to remind everyone that when you select the Guest OS for a new virtual machine

this automatically makes a selection for which vSCSI controller to use based on what drivers are available in the OS distribution.  So be sure to select the correct Guest OS to start in the right place.

Let s look at the options available today:

BusLogic – this was one of the first emulated vSCSI controllers available in the VMware platform.  The earliest versions of Windows has this driver available by default which made it easy when installing that particular OS. It wasn t however as performant as the LSI Logic driver since Windows driver was limited to a queue depth of 1, so often one would manually load the LSI Logic driver instead.  While still available and used occasionally Is anyone still running Win2K., it should be considered legacy.

LSI Logic Parallel formerly knows as just LSI Logic – this was the other emulated vSCSI controller available originally in the VMware platform.  Most operating systems had a driver that supported a queue depth of 32 and it became a very common choice, if not the default.

LSI Logic SAS – This is an evolution of the parallel driver to support a new future facing standard.  It began to grown popularity when Microsoft required its use for MCSC within Windows 2008 or newer.

VMware Paravirtual aka PVSCSI – this vSCSI controller is virtualization aware and was been designed to support very high throughput with minimal processing cost and is therefore the most efficient driver. In the past, there were issues if it was used with virtual machines that didn t do a lot of IOPS, but that was resolved in vSphere 4.1.

Are there performance differences between them.

PVSCSI and LSI Logic Parallel/SAS are essentially the same when it comes to overall performance capability.  PVSCSI, however, is more efficient in the number of host compute cycles that are required to process the same number of IOPS. This means that if you have a very storage IO intensive virtual machine, this is the controller to choose to ensure you save as many cpu cycles as possible that can then be used by the application or host. Most modern operating systems that can drive high IO support one of these two controllers.

Here s a detailed whitepaper that takes a closer look at PVSCSI vs LSI Logic SAS for IOPS, Latency and Cost.  While it does support that PVSCSI is more capable, keep in mind most customers are not producing 1 million IOPS so for real life the difference is negligible.

How many vSCSI adapters are supported per virtual machine.

It s also worth noting that you can configure a total of 4 vSCSI adapters per virtual machine.  To provide the best performance, one should also distribute virtual disk across as many vSCSI adapters as possible.  This configuration provides the capability to process more IO simultaneously and benefit from additional queues if necessary.

What about AHCI SATA.

This is a new storage controller available with vSphere 5.5 and virtual hardware 10.  It allows you to connect a large amount of storage to a virtual machine but it wasn t designed to be as efficient as the PVSCSI or LSI Logic controllers and therefore should not be used with performance sensitive applications.

Let summarize this in a chart:

Virtual Hardware Reference

PVSCSI KB 1010398.

Which vSCSI controller should I choose for performance?
  • There is a way to change from LSI logic SAS into VMware Paravirtual. Not difficult. How-to safely change from LSI logic SAS into VMware Paravirtual.
  • For those of you with your mission-critical servers already virtualized on a VMware-based virtual infrastructure, are you using the VMware Paravirtual SCSI driver to.
  • Great article, however, have you tried using scsi lsi logic with persistent data disks. i have and the result is unpleasant. every time a recompose, refresh, or.
  • SCO OpenServer 5.0 documentation covers information on how to install the operating system in a virtual machine.
  • This article includes supplemental information about configuring and using VMware Paravirtual SCSI PVSCSI adapters.

Customers who have purchased VMware vSphere 6.0 can download their relevant installation package from the product download tab below. Looking to upgrade from.

For those of you with your mission-critical servers already virtualized on a VMware-based virtual infrastructure, are you using the VMware Paravirtual SCSI driver to boost your I/O performance by an average of 12. I use it for all of my I/O intensive virtual machines, including SQL Server and Oracle VMs, and you should too.

By default for Windows Server 2008 and above, the default virtual SCSI controller is the LSI Logic SAS disk controller. It s there for compatibility purposes, and piggybacks the existing driver that is built into the operating system. It works great because it always just works.

However, compatibility does not necessarily mean fastest, and the LSI SAS driver is a pretty good performer, but VMware developed an alternative that can boost performance for virtual machines with high I/O requirements. It is called the Paravirtual SCSI PVSCSI driver, and it is included with the VMware Tools package that should be installed into every VMware-based virtual machine. This driver was designed by VMware to improve the raw performance of every virtual disk connected to it. On average, I experience a 12 throughput performance improvement, lower latency to the underlying storage, and lower CPU associated with storage handling when using this driver.

How can you take advantage of this driver.

It s easy. Virtual disks are connected to virtual disk controllers. All we have to do is ensure that the VMware Tools are installed so the driver is present and then make a few changes to the VM configuration.

First, check out the virtual disk configuration of the VM. This example uses an older Windows Server 2008R2 VM. Almost always, one or more virtual disks are connected to the LSI SAS controller. See how the disk assignments are set to a SCSI ID of 0:0 and 0:1. This is how the old SCSI hardware configuration was emulated with the advenet of virtualization. The first number is the controller number, and the second is the SCSI channel assignment.

Also notice that we only have one SCSI controller present in the VM configuration. Let s fix this. This example is performed in my lab via the vSphere Web Client on a vSphere 5.5 base system. The vSphere client update procedure on older installations is slightly different but the same concepts apply.

Gracefully shut down a virtual machine. Edit the virtual machine settings. Add a new SCSI controller. The default type is again LSI SAS. Expand the new hardware entry and change it to Paravirtual. Click OK to save the changes.

Edit the settings again. Pick a virtual disk that is not the bootable root volume I ll explain more on this in a little bit and select the virtual disk. In this case we ll pick the second virtual disk. Change the disk s SCSI assignment from 0:1 to 1:0. Click OK to save the configuration.

Now, power on the virtual machine. When Windows comes up, it will detect the new hardware and should prompt you to reboot the VM. Go ahead and do so. Once it comes up, check in the Disk Manager to make sure that the disks are online. Occasionally I have seen the disks go offline because of the change to the underlying controllers. A simple set online operation will fix this if it occurs.

Now, as always, benchmark your storage performance before and after the change to ensure that you actually do receive a performance improvement, because every system is different.

Why Not Boot Volume.

Earlier I mentioned not to use the PVSCSI driver on boot volumes. I do this intentionally. If for whatever reason there is a problem with the VMware Tools and the associated components, the PVSCSI driver could have a challenge starting up. Just once, many years ago, I experienced the scenario where the boot disk depended on the PVSCSI driver to load, but could not load to the VM could not boot. The operating system needed to boot successfully in order to properly re-load the PVSCSI driver, so it was a chicken-and-egg scenario. I have not experienced it in years, but once was enough to scar me. Keep the bootable volume on a driver that is native to the operating system, and you eliminate the remote chance of running into issues with this scenario.

Additional Tips

VMware has a great matrix of operating systems and the compatibility settings in their KB located here.

The SCSI queue depth in Windows for these disks is 64. If you need to change the SCSI queue depth in Windows beyond this value, VMware has instructions located here.

Now you can get a noticeable and measurable disk performance boost on your existing VMs with just a couple of reboots. Go forth and improve your mission-critical VM performance with this little update – for free.

Injecting SCSI controller device drivers into Windows when it fails to boot after converting it with VMware Converter 1005208.