Flash Storage: Choosing the Best

Flash storage is making big inroads in the enterprise -- but which type of flash works best for your data center?
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It’s no surprise that the enterprise data center has a storage performance problem.  Look at what the data center to contend with: raw sensor data, machine-generated data, financial transactions, big data analysis, hosted applications, R&D, mobile, social media, video, broadcasting – and that’s the short list.

Hard disk drive-laden SANs still top the storage food chain but even high-end arrays have issues around IO and latency.

Flash can remediate performance problems and many data center managers have already adopted it. Many more plan to within a 12-18 month timeframe.

The question is: are the managers choosing the best flash solution for their needs? Flash comes in many flavors. Just because it’s flash does not make it an automatic fix for your storage performance.

Flash Factors: What You Must Have

What do you look for? There are several different flash architectures to consider. Let’s look for first for the qualities that any flash installation must have.

· Flash storage needs to provide high IO processing speeds and low latency. These requirements are the point of flash but flash products differ dramatically in their performance levels.

· Flash arrays need to deliver consistent performance and media quality over time. Flash consistency can suffer as workloads grow and as flash media ages. Don’t just look at processing speeds in a pilot project; test it with production workloads. Also ask about wear leveling and non-disruptive replacement to ensure smooth operations as media ages.

· Flash arrays need to ensure data integrity. These include enterprise services for redundancy such as replication and mirroring, media quality protection, RAID (traditional and flash), and more. Hot swapping and non-disruptive firmware upgrades are also important in this space.

· Flash needs to have a reasonable cost. What constitutes “reasonable” differs radically from customer to customer. The measuring stick is cost-for-value: what does the customer need from primary storage, and when does flash meet or exceed the value of commensurate HDD performance? The good news is that flash prices are dropping, and can come in lower when measured dollar-to-dollar against clustered HDDS.

Flash Usage in the Enterprise Data Center

Flash products primarily serve Tier 0 and Tier 1 storage processing needs. High-end disk-based arrays can approach flash speeds by short-stroking fast HDD clusters, but this gets expensive – even costlier than high end flash arrays.

Tier 0 characteristics are ultra-low latency and very high IOPs for intensive storage processing. Examples of this tier include streaming sensor or scientific data, caching, in-memory compute, OLTP, and analytics. Tier 1 is also low latency and high IOPs with added storage services for data protection and management. Examples include VDI, databases, online transactions – any enterprise application that requires fast processing and storage services.

Top Flash Contenders

Server-side flash deploys at the server level as a PCIe card and/or SSDs. It mirrors active data into a local flash cache for higher active processing speeds. Administrators use server-side flash for critical applications and virtual machines.

The primary use for flash storage is in arrays. The top three categories are all-flash arrays (AFAs) with flash chips, AFAs with SSDs, and hybrid storage combining SSDs and HDDs.

All Flash Arrays using Flash Modules

Instead of housing flash in SSDs, the array maker builds proprietary hardware to house flash chips. These systems are expensive but their high performance and array-based management are good fits in intensive storage environments. Their cost also looks better when compared to high-end HDD clusters, and when dedupe and compression yield better capacity.

IBM FlashSystems 840 yields high performance and their enterprise version, V840, adds storage services. Violin Concerto also exerts flash control at the array level. This yield high performance and improves consistency of functions such as garbage collection, which is managed at the array level and not at the more fragmented SSD level. Skyera provides skyHawk, an all-flash AFA with high performance flash and storage services.

Hybrid Flash Arrays

Hybrid arrays combine SSDs and HDDs. The SSD layer acts as fast performance Tier 0 processing and the HDDs do the data storage heavy lifting. These vendors seek to provide the familiarity, capacity and long-term storage retention of disk with faster I/O performance and lower latency at the flash layer. As with other flash storage technologies, dedupe and compression will yield much more effective capacity at the SSD layer. They lack the high I/O speed and low latency numbers of their all-flash cousins but are a good jumping off point for balancing long-term storage capacity with faster storage.

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Tags: SSD, enterprise storage, Flash Storage

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