Database Reference
In-Depth Information
and test the server once the SAN team ordered the disks and the SAN vendor installed
them.
Fast-forward several weeks when the phone rings. The customer says, “Um, yea... our
first IOMETER test yielded a whopping 1,000 IOPS. We are 19,000 short of where we
need to be for this server.” What!? After troubleshooting the installation, starting with
the subsystem, we discovered the SAN team ordered enough disks to accommodate the
amount of data the SQL team said was needed, but forgot about the IOPS requirement.
After the customer reordered the right drive configuration (oops!) and put it in the array,
the IOMETER test yield far beyond the 20,000 IOPS necessary to support this database.
LSI Logic SAS or PVSCSI
It is important to understand the differences at a technical level that the different virtual
SCSI adapters provide. Out of the box, supported by Windows 2012, is the LSI Logic
SAS virtual SCSI adapter. This adapter will install without needing to have additional
drivers loaded into the operating system during the virtual machine build.
The PVSCSI adapter is a paravirtualized adapter that is aware it is sitting on the
vSphere platform, and the drivers are part of the VMware Tools install. The PVSCI
adapter will utilizes fewer physical host CPU resources compared to the LSI Logic SAS
driver, offers a configurable queue size (covered in
Chapter 6
), and can deliver better
throughput for demanding workloads.
Our recommendation is to use PVSCSI. We have seen some customers mix and match,
using the LSI Logic SAS for the Windows OS and SQL Binaries (adapter 0) and
PVSCSI for running the remaining VMDKs (databases, logs, and tempdbs).
Note
When PVSCSI was first introduced in vSphere 4.0, it was recommended
for workloads requiring 2,000 or more IOPS. This has been resolved as of
vSphere 4.1, and the PVSCSI adapter can be used for all workloads. For
more information, see
http://kb.vmware.com/kb/1017652
.
Caution
Double-check that you are running at the appropriate patch level for vSphere
because there have been updates to address an issue with Windows Server 2008
and Server 2008/R2 reporting operating system errors when running SQL Server.
vSphere versions prior to vSphere 5.0 update 2 should be checked. For more
information, review
http://kb.vmware.com/kb/2004578
.
