The storage world is undergoing a huge transition. The magic of all-flash arrays is entrancing everyone. According to Gartner, the total revenue realized from selling flash drives is going to overtake that for hard drives in 2018. Their forecast states that the percentage of data centers using only solid-state arrays for production will increase from less than 1% in 2015 to 25% by 2020. These facts force corporates to think about all-flash arrays in their next IT budget cycle plan.
The name “all-flash” implies higher performance. There is a lot more than that. I wish I could cover ‘all’ of it in just a ‘flash’!
But to truly understand the science behind them, we should first get familiarized with the traditional storage approaches and their inherent challenges.
Traditional storage approaches and associated challenges
For the past few decades, hard disk-based arrays and hybrid arrays, with a majority of hard disks, have fulfilled most of the enterprise storage requirements. The most common hard drives in use are SAS, SATA, and NL-SAS. SAS is required where high performance and enterprise features are in demand. SATA is preferred most likely for its cost-effectiveness, and NL-SAS fits in the middle of the spectrum. Invariably though, they all share similar design and working mechanism. The read and write process requires moving parts to move faster to achieve better performance. SATA may support up to 7.2k rpm but SAS can go all the way up to 15k rpm.
Business applications have operated pretty well so far, but in the dawn of server virtualization, the hard drives are under tremendous pressure.
- With virtualization, the CPU utilization has increased significantly, generating more input-output requests to storage. But hard disk array with capability to execute only limited number of operations per second causes high application latency. Poor operation speed also prohibits usage of space reduction techniques for production storage
- Hard disks were also characterized by high failure rates of drives. Storage admins used different RAID groups to protect the disks often at the cost of lower performance or capacity
- An average life of a hard disk is two to five years which accounts for more support tickets, raising maintenance costs and number of drive rebuilding tasks, increasing the operational costs.
The limitations of hard disk array reduce overall IT efficiency, affecting business productivity and strategic IT vision.
All-flash arrays use only flash or solid-state drives for storing data. flash diskAll-flash storage is entirely different in design, which is to be engineered and operated differently. Some of the key differences are:
- No moving hardware parts in all-flash storage, eradicating the restricted performance and reducing the disk failure probability.
- 2. A flash drive is nearly 10 times faster than a hard drive of same capacity
- Cells store data. Each cell holds one to three bits depending upon drive. Single-cell flash disks are expensive but perform faster and support more number of program cycles than multi-cell disks
- The write process is a little complex. Data first needs to be erased, in blocks, and then written in pages. Thus, flash is not recommended for highly write-intensive workloads.
- There are limited numbers of program-erase cycles supported in flash drives. So, the data management algorithm should promote even utilization of all the cells, rather than randomized operations as in hard drives
- Unlike older RAID methods, flash needs data protection at the cell level. In general, every flash OEM provides spare drives in their storage shelves whose cells can replace faulty cells, saving lot of effort compared to complete rebuild as in the case with hard drives.
Traditional hard disk-based storage arrays were engineered with SAS- or SATA-based interconnects. If we use 20 flash disks in an array, each delivering 3000 IOPS, it doesn’t mean 60,000 IOPS output since the controller can only support 6000 IOPS at a time, restricting the performance. Also, the data management algorithm and storage controllers were meant to handle hard drives traditionally. These design limitations make the older storage arrays unfit for use with flash drives. We should only choose grounds-up built disk array meant to operate with flash disks.
Benefits of all-flash arrays
- High performance
Majorly, all the all-flash array vendors assure consistent less than one millisecond latency. It is a drastic improvement over traditional arrays, with about 20 ms latency.
- Storage footprint consolidation
All-flash arrays come with support of inline compression, deduplication, and thin-provisioning. Some vendors guarantee the space reduction by a factor of four for any workload, except files. With the evolution of higher density drives, we may witness drastic reduction in power and hosting costs in enterprise storage.
- Automated management
Several operational activities like tier-wise LUN creation, provisioning, and health monitoring, which arise by using multiple tiers, get eliminated with all-flash arrays when used for enterprise storage. Moreover, inbuilt intelligent analytics ease enterprise storage management. A centralized dashboard provides continuous performance and health reports, and enables proactive alerts.
- Enable IT transformation
Per Moore’s estimation, CPU density increases nearly 10 times each decade. On top of it, server virtualization aids in running multiple application hosts on a single physical server. These advancements have consolidated the performance-hungry applications on relatively smaller data center space. However, storage market has not experienced any major transformation for long due to which a considerably large space is required to accommodate the storage requirements for application needs. Flash can reduce the gap between server and storage expectations.
- Lower operational overheads
A flash drive is expected to run smoothly for five-seven years or more, compared to two-five years for a hard drive. This lower rate of depletion can help reduce the support tickets for drive replacement and rebuilding. Also, high automation features would reduce the number of complex activities for a storage admin. Owing to these native design features, flash will ensure huge reduction in operational expenditure.
- Overall TCO reduction
The raw per GB cost of a flash drive is still higher than that of a hard drive even today. But when we bring into account its benefits, we can get close to 50% savings in overall TCO. As per Wikiborn, the overall TCO benefits for flash, as against hard disks, may even reach 700% by the end of 2020.
Technologies keep advancing with time and invent smarter ways to solve our needs. Gadgets like Walkman and reel camera were once the talk of the town, but are nowhere to be seen now due to the smartphone revolution. Similarly, the storage market is all set to say goodbye to spinning disks and welcome the next-generation all-flash arrays. There would surely be a time when even all-flash fever subsides and gives way to some other path-breaking technology in field of storage. Until then, all-flash array will keep on redefining the storage market.