In Part 1, we looked at disk-based storage that uses flash as a cache. Because disk-based products rely on disks as a key part of their basic data path, they have difficulty achieving flash-level latency and will be left behind by rapid improvements in flash performance.
In contrast, flash-based products are designed specifically for flash rather than mechanical disk drives, delivering dramatically lower latency. The key distinction is that their basic data paths do not require accessing disk. Often using low-cost MLC technology, flash-based products sometimes incorporate new techniques such as inline dedupe and compression to reduce the high $/GB of flash. Most flash-based products are flash-only, while some integrate hard disks to expand capacity and simplify management.
Initial flash-only products are basic arrays. Focused on getting the highest possible IOPS, they generally have very high $/GB, and are missing enterprise features such as HA, snapshots, and clones. Even with inline dedupe and compression, flash-only arrays are currently too expensive for running the vast majority of applications in an enterprise. Even very aggressive estimates for these advanced techniques cannot overcome the >15x cost/GB gap between low-cost SATA HDDs and MLC flash devices. Consequently, flash-only arrays require separate low-cost disk-based storage systems for storing snapshots, replicas, infrequently accessed data, and the data of less IO-intensive applications (Figure 1).
As a result, flash-only arrays require significant additional work to stage and de-stage data and applications between flash and disk. Combined with their high $/GB and lack of enterprise features, this means that flash-only arrays are much better suited for very high-performance applications without significant data management requirements. Using flash-only products for enterprise applications will require extensive planning, monitoring and additional supporting infrastructure.
Next-up in the series: Flash Revolution, Part 3: Intelligent flash-based products.
Previously in the series: Flash Revolution, Part 1: Disk-based flash products