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Introduction to Hybrid Storage Arrays

Hybrid storage arrays leverage a combination of spinning disk and flash disks to create systems that feature many of the performance benefits of flash coupled with the capacity benefits inherent in disk-based systems.  Remember, even as the cost of flash comes down, hard drive manufacturers continue to push physical limitations to increase the data density of spinning disks.  The result is constantly cheaper hard drives with a cost per GB that simply can’t be beat, especially if data reduction in the form of compression and deduplication are included.

How Flash is Leveraged

When used in hybrid systems, solid state disks serve as either a huge caching layer sitting in front of spinning disks or as a performance tier of storage or, in many cases, they serve both functions.  Hybrid storage devices have proven themselves to be a popular option for organizations that have experienced performance issues with spinning disk legacy storage systems but that do not yet need the raw performance that all flash arrays provide.

Flash Type Matters in Hybrid

However, hybrid storage systems – especially as the cost of flash continues to drop – are not necessarily the panacea that they once were.  For example, the flash storage in hybrid systems has to be far more resilient than it does in all flash systems.  The reason: bear in mind that flash storage cells can withstand a finite number of cycles before cells begin to degrade, making them unable to store data.  With flash used as a caching layer, there is often a very high degree of data “churn” taking place behind the scenes.  Data churn refers to the speed with which data is being changed on the disk.  The higher the level of churn, the faster that the flash media program/erase cycles are consumed.

As such, flash in these systems needs to support higher numbers of cycles and be more resilient than is necessary in lower churn scenarios.  Flash in a hybrid system needs to be top grade, which also means that it will carry a price premium.

Balanced Cost vs. Performance

Many organizations, particularly SMBs and small midmarket organizations, continue to use all disk systems and are suffering performance challenges.  Although an all flash array would handily solve these issues, some of these organizations may not need that kind of performance and are far more focused on the capacity side of the storage equation.  By buying hybrid storage system, these organizations can get $/Gb prices that trounce that of hard disk drive-based storage while paying a $/IOPS price that simply isn’t possible to achieve with HDDs alone. When HDDs and SSDs are brought together, it possible to truly balance capacity and performance needs.

Simplified Operations

Simplicity is the new black!  Rare is the CFO or the CIO that wants find ways to make a job harder to do.  Unfortunately, though, many data centers — with carefully stacked solutions — have introduced complexity to organizations that makes it very difficult to adapt to new business needs.  These organizations are looking for ways to massively simplify the computing environment.  With regard to storage, these systems haven’t always enjoyed a reputation for “ease of use” and people are tired of the status quo in this area.  The complexity problem has only gotten worse as IT departments deploy news kinds of workloads with wildly variant I/O patterns.

Hybrid storage brings to the equation the potential for massively increased simplicity in a couple of ways:

  • Depending on solution, built in, always on deduplication to maximize capacity, accelerate workloads, and minimize flash wear.
  • Newer entrants in the space have dead simple administrative options for these devices.

Hybrid Summary

Even though the market trend continues to shift to an all flash world, hybrid storage systems remain incredibly popular in places where capacity still outweighs performance needs.