Today’s All-Flash Arrays are ready for prime-time, and here’s why: flash is now much, much more than just an expensive but super-fast disk.
1. Falling costs
For a start, it is not that expensive now. Your AFA won’t use the same grade of flash as your smartphone, but it still benefits from the consumer-driven economies of scale and the waves of technological innovation that are pushing down production costs. So while flash may still be more expensive than disk per raw gigabyte, the difference is getting smaller all the time because the cost of flash is falling faster than the cost of disk capacity – and when it comes to price per IOPS, AFAs have already taken the lead.
2. Low latency
Non-mechanical flash can deliver data far faster than a disk and more consistently too, since you don’t have to wait for a read/write head to move and then for the desired disk sector to spin underneath it. Compared to disk, therefore, flash is especially good for random access.
3. Consistent quality of service
With relatively little contention and no mechanical delays, flash can deliver more consistent performance than disk. This is important when it comes to implementing features such as automated quality of service (QoS) because you can’t plan and prioritise properly without predictable performance.
4. No more wasted capacity
Regardless of the cost per gigabyte, flash can work out cheaper than disk because often you need less flash to do the job. With a disk, performance typically declines as it fills up because its data becomes fragmented. This limits the practical utilisation level, and wastes a lot of space. Flash doesn’t have this problem, so it can be pushed closer to the envelope, meaning you can actually use close to all of its total capacity.
5. In-line data reduction
Techniques such as data compression and de-duplication have been around for years, but both add latency and de-dupe requires look-up tables, so its use on primary disk was limited, for example, to relatively static datasets. With flash, its low latency means that in-line data reduction requires only a marginal performance hit, making it practical for many more business applications. Reduction ratios that can average five to one translate to significant savings per gigabyte stored.
6. Goodbye spindle-chaining
That limited IO capacity per disk spindle also means that to get more performance out of a disk array, you must add more drives – most probably many more than you needed from a capacity perspective. Flash’s IO properties are quite different, so this isn’t necessary. Result: you can do more with fewer drives, and further shrink the price differential.
7. Less floorspace, power and cooling
Flash is denser than disk – drive makers can already squeeze 60TB into a 3.5-inch SSD (solid-state drive) and plan to have 100TB SSDs by 2020. By comparison, 3.5-inch disk drives are not expected to reach 100TB until 2025. Add that using an AFA instead of a disk array often means you can solve the same problem with fewer drives (SSDs or flash modules), and you significantly reduce the need for rack and floorspace. That in turn means less power consumed, so less heat generated and a decreased need for cooling. More cost savings!
8. Quieter and more reliable
Flash is non-mechanical and therefore vibration-free, so an AFA can be quieter and more reliable than an equivalent array packed with humming disk drives. Flash’s earlier reliability issues, with memory cells only withstanding a finite number of write cycles, are a thing of the past thanks to advanced error-correction and wear-levelling software.
9. IT and business transformation
Lastly, software has traditionally been written to cater to the foibles of hardware. For instance, programmers would avoid going to disk where possible, as that was the slowest part of the system. Flash lets you build applications in new ways, for example to manipulate more data and do it faster. This in turn opens the gate for the business to accelerate its processes or work in ways that were impossible before.
Of course, flash still has a few remaining caveats – for instance an AFA will not accelerate all applications to the same degree, as it depends on their storage access patterns. However, SSDs have been around for almost four decades and flash for three decades. No one expects anything else now in a phone, media player or laptop. Sure, disks may still have data centre roles as secondary storage, but for primary storage, flash is well on its way to being the new-normal.