SSD in the Array? Today

Posted on 01/26/2015 by

Tien Shiah

We hope you’ve been enjoying our blog series.  Here’s another from us and Dell Tech Center:

By now, you have recognized that the performance gap between the CPU and hard disk-based storage systems has been increasing significantly every year. Until now, you may have even relied on popular workarounds to reduce this gap (e.g. RAID schemes and/or expensive cache memory). As this technical bulletin points out, traditional HDD storage systems increasingly struggle to meet the I/O performance requirements of data-hungry applications.

At the same time, the cost of flash storage continues to decrease. Moreover, flash storage can now be deployed in much greater capacities than cache, giving you the opportunity to reduce latency and improve overall performance. But what about using flash in an external storage array? With auto-tiering and other advancements, large amounts of flash storage (in the form of solid state drives (SSDs)) is becoming commonplace in the enterprise.

The Increasing Power and Value of SSDs

SSDs with a SAS interface are designed for use within an external storage array. They are primarily designed to handle high volume, write-intensive applications such as online transaction processing (OLTP), mail servers, and other common enterprise applications. Engineered to maximize write endurance, these drives provide long-lasting sustained performance by relying on advanced intelligence that promotes “wear-leveling” and other features required in the data center.

As an example, using industry-leading Samsung 12Gbps SAS SSDs as a second layer of cache in a storage array will help accelerate the transfer of data between a system’s DRAM-based cache and HDDs. This has the effect of reducing latency, as hot data is stored in the higher-performing flash storage cache, thereby reducing the need to read data from slower-moving HDDs. It’s ideal for systems that repeatedly access the same blocks of storage and then quickly change to repeatedly access a different set of blocks, an occurrence we often see with databases that handle online transactions.

Additionally, as the $/GB price of SSDs continues to fall, there are increased opportunities to make use of different drive types within an array. Many storage arrays include auto-tiering, a technology that stores more frequently accessed data on the fastest storage available and less frequently accessed data on slower (but typically higher capacity) storage options.

Maximizing Your Auto-Tiered Configuration

So what is key to maximizing an auto-tiered configuration? It’s knowing how much space you need. A simple way to determine this is to examine the daily amount of “data change” for the servers configured to use auto-tiered storage. If the amount of SSD storage is a little larger than the amount of data that is changing, then all of the most recently used data for any given day will remain within the SSD storage.

On some occasions, you even may consider deploying an SSD-only storage array.  While this will certainly deliver sustained performance improvements across the servers attached to the array, there are other considerations that should play a role in your configuration decisions (e.g., total capacity, cost, data protection, and redundancy requirements).

Knowing that a primary reason for choosing SSDs is performance acceleration, it would be best to first consider the business goals that are driving the decision-making process and how technology can help you achieve those goals. You might also want to refer to Samsung’s Green SSD website pages to see how SSD technology can solve your specific data center needs

Every application in your data center has different I/O requirements.  Understanding these requirements is the starting point for selecting the right SSD strategy. When TCO is a primary driver for storage selection, then flash best suits read-intensive applications with a random I/O pattern. Traditional HDDs may be more suitable for bulk storage that is infrequently accessed. In many cases, a combination of the two will allow you to maximize the advancements in flash technology while best addressing your specific needs and TCO requirements.

For more information about Samsung SSDs, please visit: http://www.samsung.com/global/business/semiconductor/product/flash-ssd/overview

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