First, it’s important to remind everyone that when you select the Guest OS for a new virtual machine:
his
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.
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 wasn̢۪t designed to be as efficient as the
PVSCSI or LSI Logic controllers and therefore should not be used with
performance sensitive applications.
Want to download this blog as a PDF document, click the link below:
https://drive.google.com/file/d/13iKhavHhg8WdEk3KqXrFe6Z3zHdYE6zO/view
https://drive.google.com/file/d/13iKhavHhg8WdEk3KqXrFe6Z3zHdYE6zO/view
Abd El-Rahman Oreiby
Senior Data Center Engineer
Al Thuraya Security Egypt
www.abdelrahmanoreiby.weebly.com
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