44 | Dell EMC VxRail Appliance Operations Guide
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While almost all data sets benefit from deduplication, typical virtual-server workloads with highly
redundant data such as full-clone virtual desktops or homogenous-server operating systems
benefit most. Compression provides further data reduction. Text, bitmap, and program files are
very compressible, and a 2:1 compression ratio is common. Other data types that are already
compressed, such as some graphics formats and video files or encrypted files yield little or no
data reduction through compression. VMs that are encrypted using vSphere encryption benefit
little from vSAN deduplication and compression.
Considerations
While the VxRail deduplication method is very efficient, some CPU resources are used to
compute the segment fingerprints or hash keys, and additional IO operations are needed to
perform lookups on the segment index tables.
vSAN computes the fingerprints and looks for duplicated segments only when the data is being
de-staged from the cache to the capacity tier. Under normal operations, VM writes to the write
buffer in the cache SSD should incur no latency impact.
Environments that benefit most for deduplication are read intensive environments with highly
compressible data. Use the figure below to determine the value of deduplication for an
application environment.
Figure 20. Value of deduplication for specific application environments
Consult with your Dell EMC or VMware VxRail specialist, who can model your workload against
a specific system configuration to help you decide if the benefit of deduplication offsets the
resource requirements for your application workload.
Enabling deduplication and compression
Deduplication and compression are disabled by default and are enabled together at the cluster
level. While deduplication and compression can be enabled at any time, enabling it when the
system is initially setup is recommended to avoid the overhead and potential performance
impact of having to deduplicate and compress existing data through post processing.
Summary of Contents for VxRail Appliance
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