Specifications

Best Practices for Virtualizing and Managing Exchange 2013
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Best Practices and Recommendations
Using differencing disks and dynamically expanding disks is not supported in a virtualized
Exchange 2013 environment. The thin-provisioned nature of the dynamically expanding VHDX file
means that the underlying storage can become overcommitted. As each dynamically expanding
VHDX file grows in size toward its configured maximum, the underlying storage could run out of
space if not carefully monitored. Instead, fixed-size VHDXs can be used to allocate a static amount
of space on the underlying physical storage upfront, thereby ensuring that there will be enough
storage space.
To reduce disk contention, do not store system files on hard drives dedicated to storing virtual
machines.
Do not use snapshots for the virtual machines in a Exchange 2013 production environment. When
you create a snapshot, Hyper-V creates a new secondary drive for the virtual machines. Write
operations occur on the new drive, and read operations occur on both drives, resulting in reduced
performance.
Be aware of underlying disk read/write contention between different virtual machines and their
virtual hard disks.
Virtual IDE vs. Virtual SCSI
Virtual machines can be configured to use virtual IDE device controllers or virtual SCSI device controllers
to connect virtual storage. When a virtual machine starts, the virtual IDE controller is used with a boot
VHD/x file because the virtual SCSI disk requires a driver to be present during boot-up. This driver is only
present when booted into the operating system. IDE is limited to 3 connected disks. (One port is retained
for the DVD drive, which is required for updating the integration components.) Virtual SCSI, on the other
hand, can have 64 connected disks per controller and 4 controllers per virtual machine, giving a total of
256 virtual SCSI disks per virtual machine. Virtual SCSI also supports hot-add/removal of disks, whereas
virtual IDE disks do not.
Best Practices and Recommendations
The virtual IDE controller must be used for booting the virtual machine; however, all other drives
should be attached to the virtual SCSI controller. This ensures optimal performance, as well as the
greatest flexibility. Each virtual machine has a single virtual SCSI controller by default, but three
more can be added while the virtual machine is offline.