This is part of an ongoing series of longer articles I am posting every Sunday.
The tech industry has been buzzing about solid state drives (SSDs) again lately, but many questions remain. Even after many major vendors (Apple, EMC, and Dell to name a few) have introduced NAND flash-based disk into their core products, it is unclear whether non-disk storage will fly or flop. I’m betting it will find a nice niche, but that traditional spinning disks are here for a good long time.
Apple’s Flashing Success
When Apple switched from hard disks to flash in their mainstream product line, the world was abuzz with the novelty: Would flash displace hard drives? Sure, the company still offered disk-based storage for those needing vast capacity, but most people found that 8 GB or so of storage was plenty for daily use. Of course, instead of the MacBook Air, I’m talking about the iPod family, which contains just a single disk-based model.
Like the Air, the iPod demonstrates that what matters in the “take it with you” market is portability in the form of low weight, perceived durability, and compact dimensions. And NAND flash excels when it comes to packaging. The flash-based iPod is an excellent semaphore for this market segment in other ways, too. Audio files are fairly small, so music users don’t need all that much storage, relatively speaking. They will gladly ignore the cost per GB, too, at such small capacity points: iPod Nano buyers pay ten times more per GB than iPod Classic buyers.
In the case of the iPod, the compact size and joggable durability afforded by the flash iPods is worth the money to most buyers, not that flash player has sufficient capacity to meet their needs. The MacBook Air teaches a slightly different lesson: Although reviewers are quick to point out that the speed and battery life difference between the hard disk and NAND flash versions of the mini notebook are negligible, early buyers were happy to pay $1000 extra to skip the disk. In this case, they paid for quick access time, light weight, and durability that exist as much in their perception as in real-world benchmarks.
EMC’s Heavyweight Champion
In the exact opposite corner of the data storage world lurks EMC’s top-line Symmetrix DMX storage array. When the company announced the availability of NAND flash drives as their top-tier choice for storage, it turned the heads of the whole enterprise storage industry. Although the technology implementation is substantially different from Apple’s iPod, EMC’s move suggests that another group of customers exists who are similarly unimpressed by a low cost per GB: Enterprise application managers.
Many have suggested that enterprise flash is not yet competitive in terms of price, capacity, reliability, or even performance. And they have publicly disagreed with EMC CEO, Joe Tucci, who claimed effective parity after 2010 at last year’s EMC World event. After all, today’s enterprise flash drives are far more than ten times more expensive than their spinning brothers, and disk capacity continues to march higher by the month.
But the comparison is not about the cost of apples or oranges. In the enterprise storage space, flash drives sot at the top of the pyramid, with just a few units added into the traditional tiered storage mix as a “tier zero” of maximum performance. It is not as simple as pulling out a set of 146 GB FC drives and replacing them with a similar number of flash units. Instead, a few key applications or data sets are migrated up to the pinnacle, with the rest of the stack remaining the same.
There is huge promise when this tiered model is combined with storage virtualization, especially the automated variety. If the tiny percentage of storage that truly needs top-tier performance could be moved to a few solid state disks, the whole stack will benefit from reduced device contention. If automation could make the decision on a block-by-block basis, the effectiveness would be much greater.
I Still Remember
There is another kind of solid state disk in play, too. For over two decades, company after company has pushed the idea of packaging high-performance DRAM as a disk substitute for enterprise storage, just as EMC has now done with NAND. These RAM-based disks offer even higher performance and prices than their flash-based cousins, and none has taken the industry by storm.
Way back when a tiny EMC was one purveyor of solid state storage, I recall the philosophical conundrum posed by the devices: Is it better to package DRAM as storage and use it in a conventional manner or to use that same memory as a cache for actual disks? The market voted for the latter, with EMC and others introducing in-array cache to accelerate RAID to great effect. System memory expanded in parallel, with modern servers optimally caching data in three or more levels internally as well.
Where Does the Flash Go?
For most uses, this is precisely the correct configuration. The priciest and quickest “storage” is placed close to the CPU, with performance and cost dropping and capacity increasing as one moves outward.
Where does flash belong, then? Apple teaches us that NAND flash delivers the goods when it comes to the portable market, and it is likely that the use of this technology in this area will only continue to grow. And EMC shows that there is a need for higher performance in the enterprise storage world as well, though perhaps not enough for pure DRAM devices.
The message is clear: As long as the cost of disk continues to lead, NAND flash will remain a niche product. There are certainly markets for NAND-based devices, from portable computing to the enterprise, but disk just works too well to be displaced. While one can never see too far into the future of storage, it seems clear that conventional hard disks will remain the dominant media for a few more generations of technology at least.