User guide

© 2011 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information. Cisco Validated Design Page 30
For more information on deduplication, refer to NetApp TR-3505: NetApp Deduplication for FAS, Deployment and
Implementation Guide
3.4.5 Performance
Virtual desktops can be both read and write intensive at different times during the lifecycle of the desktop,
depending on the user activity and the desktop maintenance cycle. The performance-intensive activities are
experienced by most large-scale deployments and are referred to as storm activities such as:
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Boot storms
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Login storms
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Virus scan and/or definition update storms
With physical desktops, this was not a problem as each machine had its own disks and I/O was contained within a
single desktop. With Citrix XenDesktop using a shared storage infrastructure, significant performance issues
might arise during these critical operations. This essentially means the solution would require a large number of
additional spindles to meet the performance requirements, resulting in increased overall solution cost.
To solve this problem, the NetApp solution contains transparent storage cache sharing (TSCS). Transparent
storage cache sharing is a core component of Data ONTAP and is extended with Flash Cache (or PAM). These
solution components save customers money by:
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Requiring far less disks and cache
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Serving read data from cache freeing up disk I/O to perform writes
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Providing better throughput and system utilization
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Providing faster response times and a better overall end user experience
3.4.6 Transparent Storage Cache Sharing
Transparent storage cache sharing (TSCS) allows customers to benefit from NetApp‘s storage efficiency and at
the same time significantly increase I/O performance. TSCS is natively built into the Data ONTAP operating
system and works by using block-sharing technologies such as NetApp primary storage deduplication and
file/volume FlexClone to reduce the amount of cache required and eliminate duplicate disk reads. Only one
instance of any duplicate block is read into cache, thus requiring less cache than traditional storage solutions.
Since Citrix XenDesktop implementations can see as great as 99 percent initial space savings (validated in the
NetApp solutions lab) using NetApp space-efficient cloning technologies, this translates into higher cache
deduplication and high cache hit rates. TSCS is especially effective in addressing the simultaneous system boot
or ―boot storm‖ of hundreds to thousands of virtual desktop systems that can overload a traditional legacy storage
system.
The following are the main benefits of transparent storage cache sharing:
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Increased performance: With transparent storage cache sharing, in combination with FlexClone and
deduplication, latencies decrease significantly by a factor of 10x versus serving data from the fastest
spinning disks available, giving sub millisecond data access. Decreasing the latency results in higher
throughput and lower disk utilization, which directly translate into fewer disks reads.
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Lowering TCO: Requiring fewer disks and getting better performance allow customers to increase the
number of virtual machines on a given storage platform, resulting in a lower total cost of ownership.
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Green benefits: Power and cooling costs are reduced as the overall energy needed to run and cool the
Flash Cache module is significantly less than even a single shelf of Fibre Channel disks. A standard disk
shelf of 300GB 15K RPM disks can consume as much as 340 watts (W)/hr and generate heat up to
1394BTU/hr. In contrast, the Flash Cache module consumes only a mere 18W/hr and generates 90BTU/hr.
By not deploying a single shelf, the power savings alone can be as much as 3000kWh/year per shelf. In