Deduplication, HDDs and SSDs: Achieving the Right Balance in VDI Deployments

Virtual desktop infrastructure (VDI) is emerging as one of the hot trends for 2011 and beyond. But successful VDI deployments, especially large ones, do not happen by accident and deduplication and solid state drives (SSDs) are now viewed as key technologies to deliver on a successful VDI deployment. The trick is identifying an appropriate and risk-averse way in which to implement these technologies without incurring some of the unpleasant side effects they can cause.

Deduplication and SSDs are becoming viewed as prerequisite technologies to ensure successful VDI deployments for two primary reasons.

  • There is a substantial amount of duplication of files when migrating desktops to VDI environments. This creates a need for a large amount of storage.
  • Booting a desktop requires reading from the disks on which its images reside. It is when multiple desktops are booted at the same time that contention occurs and performance is negatively impacted.

Deduplication and SSDs can be used in combination to tackle these VDI issues head on. Deduplication technology minimizes the storage growth associated with VDI deployments as only one instance of the duplicate data needs to be stored. Further, by storing deduplicated data on SSDs, data can be read back much more quickly plus SSDs can potentially become a cost-effective alternative to disk if less data is stored on them.

However there are other factors that come into play when deduplication and SSDs are implemented that are not always apparent that can negatively impact a VDI implementation.

  • Write I/O performance to SSDs is not nearly as good as read I/Os. SSD read I/O performance is measured in microseconds. So while SSD write I/O performance is still faster than writes to hard disk drives (HDDs), writes to SSDs will not deliver nearly the same performance boost as read I/Os plus write I/O performance on SSDs is known to degrade over time.
  • SSDs are still 10x the cost of HDDs. Even with the benefits provided by deduplication an organization may still not be able to justify completely replacing HDDs with SSDs which leads to a third problem.
  • Using deduplication can result in fragmentation. As new data is ingested and deduplicated, data is placed further and further apart. While fragmentation may not matter when all data is stored on SSDs, if HDDs are still used as part of the solution, this can result in reads taking longer to complete.

These issues illustrate how simply deploying deduplication and SSDs in conjunction with VDI may not be sufficient to avoid other issues that can ultimately undermine a successful VDI deployment. So what organizations need to do is select solutions that include deduplication and SSD as features but implement them in such a way that these features do not eventually become issues in VDI deployments.

Symantec VirtualStore is one such product that has taken some steps to do exactly that as VirtualStore can virtualize any tier of disk to create a storage pool for VDI implementations that can include both HDDs and SDDs as well as deduplicate data stored to them..

Virtualizing HDDs and SSD in this fashion and then deduplicating data stored on them helps to delivers the fast performance times that VDI needs during boot times when data is read while facilitating the continued use of more economical HDDs to store less frequently accessed data.

Further, engineering efforts are afoot within Symantec that will soon enable the placement of deduplicated, commonly accessed blocks of data on SSDs. This will eliminate the need to  read this data from HDDs and thereby improve performance even more.

Deduplication and SSD technologies are fast becoming viewed as key technologies to leverage in enterprise VDI implementations. But the mere introduction of these technologies into VDI environments does not translate into their effective and optimized use nor should it negate the use of HDDs.

By Symantec VirtualStore taking advantage of the best of what deduplication, SSDs and HDDs have to offer and implementing these features, users can get the storage efficiency they seek, the performance they need and the economics to justify its deployment in their VDI environments.

Jerome M. Wendt

About Jerome M. Wendt

President & Lead Analyst of DCIG, Inc. Jerome Wendt is the President and Lead Analyst of DCIG Inc., an independent storage analyst and consulting firm. Mr. Wendt founded the company in September 2006.

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