Until recently storage choices were simple. The technology was the venerable hard disk array, either SAS for higher performance or SATA for slower but cheaper bulk storage. The basic calculation for all applications was $ per Gbyte, since all disk drives offered the same number and speed of IOPS within a narrow range. The main issue was how much storage does the company need and how fast is that growing.

The introduction of persistent flash storage, coming out of the consumer electronics industry, has created additional important choices that offer new opportunities but also complicate the storage decision process, writes Wikibon Analyst, Founder & Managing Consultant of the 1610 Group, and former CIO Scott Lowe in his latest Wikibon Alert, Flash vs. Hybrid vs. HHD Decision Points. Basically flash offers order-of-magnitude faster read and write speeds and numbers of IOPS but at a significantly higher absolute cost. Lowe discusses the basic issues and provides the core calculations that SMB CIOs should make to choose the right solution for their present and future needs — all-disk, all-flash, or hybrid.

From a cost perspective, disk systems provide much lower cost-per-Gbyte, while flash provides much lower cost-per-IOPS. That plus the order-of-magnitude faster absolute speed of flash makes it the choice where IOPS is critical but a very expensive alternative for applications that can perform adequately with the lower speed and IOPS of a disk array. Global companies often use flash for high-demand data and disk for archiving older data with lower demand and where read/write speeds are not critical.

One issue that makes the decision different for most SMBs than for large enterprises is that SMBs typically use a single array to support all the applications in their data centers. This can lead to the necessity to make some compromises. For instance, if all the applications in the data center can operate at adequate speeds on spinning disk arrays, then the choices become fairly simple. But if a new major application — for instance VDI — that will put major demands on IOPS and data read/write speeds, is planned, the organization may need to consider flash. However, the order-of-magnitude higher cost of an all-flash array would make it a very expensive choice for supporting the rest of the data center. In this case the organization might consider either a hybrid drive or an array that can be upgraded to hybrid status with the addition of flash at a later date.

Hybrid drives are a compromise between pure disk and pure flash solutions. The flash acts as a large cache for high demand data, and the systems can be tuned to favor data for specific applications. Everything else goes on disk. That could allow an SMB to run an environment that includes, for instance, VDI or some more exotic application such as currency or stock trading, where microseconds count, along with the normal background applications that are happy on disk, in one array. Their purchase and operating costs are also intermediary between the two types of “pure” systems.

Lowe provides clear examples and calculations that can allow SMB CIOs to make the right decision for their companies. Of course once the CIO decides on which type of array he needs, other, more granular concerns must be considered in making the final choice. Fortunately, Lowe writes, numerous variations on the basic choices are available from quite a few traditional and start-up vendors in today’s market.

Like all Wikibon research, this Alert is available in full without charge on the Wikibon Web site. IT professionals are invited to register to join the Wikibon community. Membership allows them to post their own questions, tips, and research, as well as comment on published research on the site. Members also receive invitations to the periodic Peer Incite Meetings at which their peers present on how they are using advanced technologies to solve business and technical challenges.