Tip

Taking another look at solid-state disk

What you will learn from this tip: The price of solid-state disks over the past few years has decreased dramatically. This tip outlines how this price change has changed the way many companies use solid-state disk.


Solid-state disks (SSDs) are fast, compact, cool-running and reliable -- the ideal storage medium, in other words, except for one little thing… cost. These arrays of semiconductor memory organized as disk drives are tens to hundreds of times more expensive than hard disks of equivalent capacity. That's why they are what you can call "niche" products in storage.

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However, the niche has expanded dramatically in the last year as the price of SSDs has dropped due to improving technology and greatly expanded chip storage capacity. To be blunt, if you haven't looked at SSDs in the last two years, everything you know about their economics, and much of what you know about the technology, may very well be out of date.

The drop in price in the last year has been dramatic. Currently, flash memory from Samsung costs about $30 per gigabyte (GB). A year ago, it was roughly $55 per GB. That is one of the reasons that Samsung increased the capacity of its SSD for laptops from 16 to 32 GB between announcing the device last spring and showing it at this spring's CEBIT trade show in Germany.

Of course, that is a long, long way from the per GB price of a conventional hard disk. So much so, analysts have questioned Samsung's decision to bring out laptop SSDs, which are expected to sell at 10 to 15 times the price of a hard disk of similar capacity. However, it is a huge improvement on the price of SSDs, compared with their price even three or four years ago.

The strategy for employing SSDs in enterprise storage is still to use them to speed up applications and processes, improving performance without adding additional servers. However, the places where they can be used have expanded as the price has dropped and SSD vendors -- such as Silicon Systems, Texas Memory Systems and BitMicro, among others -- have brought out products geared more toward the general SAN user.

There is no question SSDs are fast. Texas Memory cites Iometer benchmarks of 250,000 random I/Os per second at a 2 K block size. With a 64 K block size and higher, the company claims its RAMSAN 320 SSD provides 1500 megabytes per second. These tests are performed using purely random data on a configuration connecting 8 servers to the RAMSAN 320 with 8 Fibre Channel links.

Texas Memory's test configuration gives an indication of how to use SSDs most effectively. One of the most potent applications today is to use SSDs as a kind of 'super cache' to speed up access to files or blocks on heavily loaded systems, especially over a SAN. In these applications, the SSD allows using cheaper, lower performance disk arrays in place of a highly tuned system with a lot of fast spindles. Generally speaking, any mission critical application that requires fast access to a lot of mostly random data is a potential candidate for SSD acceleration.

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About the author: Rick Cook has been writing about mass storage since the days when the term meant an 80 K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last 20 years, he has been a freelance writer specializing in storage and other computer issues.
 

This was first published in March 2006

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