Putting money on solid state
- By John x_Zyskowski
- Feb 18, 2001
The best way to speed up a sluggish software application is to run it on a computer with a faster processor, right? Not always. Increasingly, the problem is not processor speed but rather mechanical disk drives that can't read and write data fast enough to keep up with ever-quicker processors and database systems.
One solution is a classic information technology tale of the old becoming new again. This particular hero is a mainframe-era storage device called solid-state disk, which has been reborn in a much more affordable, convenient form. The devices, which can access data hundreds of times faster than traditional hard disks, are being rediscovered by a new generation of IT professionals for uses throughout the government, at agencies ranging from NASA to the Navy.
"They're becoming more popular for the simple reason that they can solve a real problem that a lot of organizations might face," said Dave Hill, research director for storage and storage management at Aberdeen Group Inc., Boston.
Solid-state disks earn their keep by storing the handful of frequently used files (typically about 5 percent of the total) that are the biggest causes of input/ output, or I/O, bottlenecks. Those common traffic jams occur when a server's central processor has to wait for disks to complete a read or a write before it can move to the next transaction.
But by relocating those few key files from traditional disk drives to a speedy solid-state disk, application performance often can be increased by as much as half. That can mean putting off the purchase of an expensive new server — not to mention the cost of managing it — in search of the same performance boost.
Actually, solid-state disks aren't disks at all. They are banks of dynamic RAM chips packed into a cabinet and configured to appear to a server (or mainframe, as in the early days) as just another storage device containing disk drives. Solid-state disks usually contain one mechanical disk drive, but its purpose is to act as a battery-powered safety net, where data can be stored temporarily in case an electrical failure shuts down the memory chips.
"Solid-state disk is probably the best-kept secret in IT right now," said Roy Hand, program director for command, control, communications, computers and intelligence systems at BTG Inc., a government-focused integrator in Fairfax, Va. "I can't think of a single enterprise system that couldn't have its performance improved by using" solid-state disks.
If the benefits are so great, then why not store all your data on solid-state disks? In a word, price. At about $10 to $15 per megabyte, solid-state disks are far more expensive than traditional hard drives, which cost less than 5 cents per megabyte.
"To put everything on solid-state disk would make a lot of database and system administrators' jobs a whole lot easier, but you'd have a difficult time trying to cost-justify it," said Craig Harries, vice president of marketing and alliances at Imperial Technology Inc., a solid-state disk manufacturer in El Segundo, Calif. "That's why customers typically cost-justify them just on that 5 percent of files that are most worthwhile."
An alternative way to boost server performance would be to increase the amount of the server's internal main memory, a tempting option in these times of ever-decreasing memory prices. The drawback is that if the server crashes or locks up, data in the memory is lost, too. Solid-state disks, as stand-alone devices with their own backup capabilities, do not share that vulnerability, Hill said.
Imperial Technology, which has a number of federal customers, sells the majority of its products for use in enterprise database systems. The most common files stored on solid-state disk are indexes, which are simply pointers to other information in the database, and redo logs, which are where databases make records of every transaction they perform. Some organizations are also beginning to store more specialized databases on solid-state disks, such as e-mail message transfer agents.
Even though today's solid-state disks are relatively expensive, they're a far cry from the old mainframe days, when they cost as much as $10,000 per megabyte. And price has not been the only thing slashed. Fifteen years ago, solid-state disk units were about the size of a refrigerator. Now manufacturers such as Imperial Technology and Solid Data Systems, Santa Clara, Calif., offer rack-mounted models about the size of a pizza box. That makes them well suited for space-conscious agency data centers.
In fact, one of the hottest uses in the government for solid-state disks is to support server consolidation, Hand said. As the government tries to save money by centralizing its IT operations on fewer, more manageable computers, it also ends up concentrating its data traffic, making I/O bottlenecks more common.
"That's the one downside to consolidation, but solid-state disk overcomes that and makes the whole thing possible," Hand said.
Reasons to go solid state
* Your application server is I/O bound. This means that during peak load times, jobs are backing up at your server's processor, which must wait idly for disk drives to finish reading or writing data from a previous transaction before moving to the next one.
* The I/Os are skewed. A small percentage of your files must drive a large percentage of the I/O activity. If files are not skewed this way, then you can't isolate the most frequently used ones for placement on solid-state disk. In that case, you would probably get more bang for your buck by connecting more disk drives to the server and spreading the data around to better handle the more random nature of your data access.
"In some applications, 40 percent of [CPU] time is spent waiting for disks to respond," said Mike Casey, vice president of marketing at Solid Data Systems, a solid-state disk vendor in Santa Clara, Calif. "Solid-state disk makes your server more efficient.
"Our customers can do four times as many transactions per day for the same server investment," he said. "Look how much you can save by buying one server instead of four.