Alan Atkinson is vice president and general manager of Dell Storage.
The exponential growth of data and the need to access it put huge demands on storage infrastructures. According to IDC, businesses’ storage demands are growing in excess of 50 percent a year while their total available storage capacity is growing at barely half that rate, presumably due to cost constraints.
Meanwhile, virtualization and the explosion of I/O-intensive applications for big data analytics, database transactions, and more have given IT leaders and their end users an appetite for higher levels of storage performance. CIOs have to choose between performance and cost, and increasingly, those choices are becoming more challenging to call.
Between Moore's Law and technologies like virtualization, cloud and flash memory, the IT industry is consumed by a “new, better, best” mentality, with a tendency to discard “old” technology, even though it continues to provide useful service.
Unfortunately, a complete “rip 'n replace” strategy can be more expensive and a lot more complex. It makes the most sense to add new technology, like flash and tiering, to an existing infrastructure to address new demands, improve performance or lower costs for existing applications.
Technologies like flash, or solid-state memory, and tiering have evolved to the point where, when combined, they are proven cost-efficient for the data center. They provide the speed, agility, flexibility and cost-efficiencies that are the alternative to a full "rip and replace." And, when deployed intelligently, users can get flash performance at the price of disk today.
The Fastest Storage Medium
Flash is the new high performance leader, which comes in a variety of flavors, each delivering significant advantages over high end hard disks (HDDs). Disk is not going to disappear anytime soon, but it will be relegated to less demanding work over time.
Flash benefits range from cost for performance – the dollar per IOPS (input/output operations per second) is over seven times cheaper for flash than for HDDs – to lowering rack space and power consumption costs. Beyond the infrastructure, flash also boosts employee productivity and helps meet business critical SLAs.
When IOPS is the key metric, then flash clearly outperforms disk. While a conventional 15k HDD can deliver approximately 200 IOPS, a single SSD can provide thousands of IOPS in the same form factor.
The two most popular flash technologies are single-level cell (SLC) and multi-level cell (MLC, or enterprise-class eMLC). SLC is ten times more persistent with three times faster sequential write, comparable sequential read, and more than four times the cost of MLC. Flash storage also comes in various formats and is being deployed in both all-flash and hybrid – a mix of flash and HDD – models and inside servers (i.e. PCIe cards), as well.
Enterprise adoption is growing with 30 percent already using solid-state storage and another 32 percent planning to deploy it. Forrester expects that flash will become ubiquitous in transaction-heavy environments, not just performance-sensitive ones, in the near future.
Disk's Day is Not Done
Though all-flash storage excels in high-performance use cases, disk and hybrid systems will continue to serve major roles in data centers. Disk will be around for at least another decade and will continue to complement flash-based storage for applications like databases and email and for supporting virtual server environments.
While all-flash arrays compare favorably to enterprise arrays with high performance hard drives, they do not compare favorably to high capacity hard drives.
Unstructured data growth dictates the need for dense, affordable bulk storage of less critical data that disk drives most affordably support. Unless you are having thousands of people access the same file at the same time, like in a web front application, hard drives still make sense.
Tiering Delivers the Best of Both Worlds
Tiering enables CIOs to seamlessly bridge the price/performance chasm and assign data and applications to the most appropriate storage medium. It involves assigning different categories of data to different types of storage media to ensure optimal performance and the lowest total cost.
Tiering can be considered the equivalent of an automated workflow that knows which “packages” of data require “immediate express delivery” and places them on that first tier (in this instance, flash) and which “packages” of data can be safely stored on less expensive and slightly slower second tiers. Not only can tiering allocate data between the different media, but innovative vendors have developed the capability to also automatically allocate data across write-intensive SLC and read-intensive MLC SSDs. It improves performance for data-intensive applications and workloads in a high-performance storage solution that can achieve over 300,000 IOPS.
The ability for a storage array to automatically tier across multiple SSD drive types is new and quite revolutionary with numerous advantages. While many available flash arrays leverage write-intensive SLC drives, a balance of MLC and SLC offers customers greater overall cost for performance. Overall flash reliability is increased when an array leverages the more vulnerable MLC flash tier mostly for reads. Capacity of the more expensive SLC tier can be kept to a minimum, just large enough to handle inbound write traffic. As a result, this model dramatically reduces the overall cost to implement flash.
The attraction of all-flash arrays is the predictable nature of performance. Users do not have to worry about a tier or cache miss causing data to be served from hard disk, but, without tiering, this comes at a high cost.
To be clear, all flash without or even with tiering does not solve all storage challenges alone. The latest vendors offering only all-flash arrays today typically lack full enterprise-class features (e.g. advanced replication, replays and management) and industry integrations that the more established vendors offer. There’s also significant cost savings by adding new capabilities to a user’s existing storage environment, avoiding the costs associated with the “rip ‘n replace” strategy mentioned earlier.
A storage infrastructure that allows you to easily morph into a hybrid array, one that mixes SLC, MLC and disk, can further reduce costs and increase capacity -- offering a much lower price point per/GB than all-flash arrays while providing the performance of flash. As a result, users are able to get flash performance when it’s needed, and do so at a price that’s comparable to an all-disk solution.
While flash is growing in adoption, the real value is on tiering that optimizes every application and every volume to best meet the combination of price and performance. It gives users the best of both worlds: data is written to the fastest tier using SLC drives and as data ages, the data is automatically moved to MLC drives, and eventually to slower and much less expensive traditional HDD drives.
By taking this innovative approach and adding new capabilities to their existing storage infrastructure, users are finding they can get the flash performance they need when they need it, and have improved storage performance while staying closer to the cost of a disk solution.
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