CHAPTER 2 Discovering Virtual Desktop Infrastructure 29
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and compression services, you'll find that VDI workloads tend
to reduce by high ratios thanks to the uniformity of the envi-
ronment. In some cases, you may see a 50–90 percent capacity
reduction.
Keep in mind the RAID level of the storage you intend to use. For
example, if you intend to deploy VDI into an environment with a
RAID 1 configuration, you instantly lose 50 percent of your raw
storage capacity (and take a performance hit — read this:
www.
techrepublic.com/blog/the-enterprise-cloud/calculate-
iops-in-a-storage-array/).
In this section, the capacity figures
refer to post-RAID usable capacity.
As you calculate storage capacity needs for your VDI cluster,
consider these variables:
»
The cloning method: Full clones need disk space immedi-
ately whereas linked clones need only a fraction of the raw
capacity. Capacity needs will grow over time.
»
The RAID level in use. I mention this in the preceding
Technical Stuff. Don't forget it!
»
The storage's data reduction capabilities: VDI workloads
reduce very well, so if your storage includes data reduction,
plan to see a high level of efficiency.
»
Ongoing growth needs for linked clones: Linked clones'
storage capacity needs grow over time as they drift further
from the baseline configuration of their parent virtual
machine. VMware provides formulas (also applicable to
Citrix) to help you estimate the storage capacity: (https://
docs.vmware.com/en/VMware-Horizon-7/7.9/horizon-
virtual-desktops/GUID-01B2506F-401E-4DA9-942C-
311FB1F727EE.html).
TABLE 2-2 VDI Storage Options Compared
Factor Direct/Local NAS/SAN HCI
Cost Low Medium-high Medium
Complexity Low Medium Low
Performance High Medium-high Medium-high
Scalability Low High Medium-high
