Making the case for solid-state storage

Interest in solid-state storage is high, and with a variety of solid-state implementations available and newer technologies emerging, it's time to take a serious look at how solid state could enhance your storage environment.

Data storage professionals considering solid-state storage have myriad solid-state storage architectures to consider, including systems that use solid-state drives (SSDs) in various form factors, caching implementations and appliances. If that wasn't enough to ponder, those planning on implementing these systems need to decide whether to use a product that mixes solid-state storage and traditional disk drives, or to use SSD-only storage subsystems.

But perhaps more important than just choosing the hardware, enterprises need to decide what data to put on solid-state storage or consider using some form of software automation to move the data onto solid-state storage to make the most efficient use of what is still a somewhat expensive resource. Deciding what data to place on solid-state storage and how to put it there makes choosing a solid-state storage option more complex, but your selections will have a long-term impact.

Solid-state-only shops: Not so soon

In a few decades, some form of solid-state storage may be the dominant and possibly only form of enterprise data storage. But given the present state of matters, that day is (at best) on the distant horizon. We might dream of replacing all of our electro-mechanical disk drives with solid-state storage if cost weren't a factor, but there's nowhere near enough semiconductor fabrication production capacity available today to satisfy the total storage capacity that's deployed in IT shops.

But there are some promising signs. Enterprise solid-state storage prices are dropping relative to enterprise hard disk drives (HDDs). Not that long ago, enterprise solid-state storage was as much as 40 times the price of an equivalent capacity of enterprise hard disk drive storage. The price comparison ratios are in the neighborhood of 25% to 50% of that today, depending on specific solid-state storage products.

As a result of this pricing and capacity disparity, data storage managers and administrators are finding that solid-state storage complements existing traditional forms of storage. They've deployed, or are planning to deploy, solid-state storage where high performance, low latency or energy savings are needed.

There are two basic ways to implement solid-state storage technology:

  • Use solid-state storage directly as a primary store
  • Use solid-state storage as a cache in front of spinning disks

Each of these implementations has its advantages and disadvantages, and implementations vary among storage vendors. And some vendors offer one implementation now while planning to offer the other in the next six to 12 months.

Solid-state storage comes in a variety of form factors, including nearly all the disk-drive form factors, as internal modules within a storage system or as a PCI Express bus card. The PCI Express bus form factor provides the potential for very high bandwidth storage access within a server or workstation.

Enterprise solid-state drives are available in 2.5-inch and 3.5-inch drive form factors that are compatible with today's servers and storage systems. The primary interfaces for these are SATA, SAS and Fibre Channel (FC). The SATA interface is available for many solid-state drives, especially for the consumer and desktop market. Fibre Channel has a long future as a SAN interface, but is approaching end-of-life as a disk drive interface. Disk drive suppliers and solid-state storage suppliers are moving away from Fibre Channel as a drive interface in favor of 6 Gbps SAS as an enterprise drive interface. We expect the Fibre Channel interface on 3.5-inch drives to stick around for a while to maintain spare parts on the relatively large number of 3.5-inch FC drives in enterprise disk subsystems. And we also anticipate that relatively few 2.5-inch enterprise drives will have a Fibre Channel interface.

This was first published in June 2010

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