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Solid State Storage: How It Works (Page 1/4)

Posted: July 25, 2000
Written by: Tuan "Solace" Nguyen


Welcome back to the next installment of the How It Works series. Recently, we’ve been covering storage technologies. We started out with hard drives then went into optical technology, and then holographic storage. What could we possibly come up with next? I bet some of you right now are thinking “solid-state” technology. Well, holographic storage is a type of solid-state technology. But the most common one would be a hard drive made entirely of RAM modules.

Let’s begin with solid-state hard drives.

Why Solid-state?

Why build extremely expensive equipment when 7,200RPM hard drives are dropping in price and offer large capacities? Let’s take a look at an analogy for a second. If you were to walk to the can to do stuff (heh), wouldn’t that take longer than if you could do stuff at the can while sitting where you are? If information can be accessed without having to move around to find it, then obviously data access time is greatly reduced.

The above diagram illustrates the massive speed advantage that a solid-state hard drive has over a conventional hard drive. You can expect performance gains that are 100 to 200 times that of today’s fastest Ultra2 SCSI hard drives, and those drives are already screaming fast.

Speed is only one of the advantages of using solid-state technology. Another advantage is reliability and durability. With solid-states drives you don’t have to worry about vibration and shock. Because there are no moving components, vibrations won’t affect the device.

Solid-state Hard Drives

The following picture illustrates the basic components of a typical solid-state hard drive.

This type of hard drive is made up entirely of RAM modules. They are stacked and connected in an array. It uses standard SDRAM modules to store information. But if you remember or know, SDRAM is volatile memory, meaning it loses its information when there is no power. That is why there is a rechargeable lithium-ion battery that sits in the back of the casing powering the drive when AC power is unavailable.


A high-end conventional hard drive has an I/O rate of about 60 to 90 IO’s/sec. A solid-state disk in comparison can range from 5000 to 9000 IO’s/sec.

A high-end conventional hard drive has an average access time of 6 to 8 milliseconds. A solid-state disk in comparison has an average access time of 50 to 100 microseconds.

As you can see, the benefits of having solid-state technology become more and more apparent as you look at the speed advantages it brings. Applications like video editing and mission critical issues can take advantage of the speed benefits.

Click for an actual size image.

As you can see, the drive is basically just made up of many SDRAM modules. The big black thing at the back would be the supporting battery.

Solid-state hard drives are incredible performers, but have one glaring problem -- price. The prices for SDRAM modules are still much more expensive than a conventional hard drive megabyte for megabyte.

This type of technology has been out for a long time. They exist in PCMCIA cards, flash cards, etc. The Diamond Rio and Creative Labs Nomad would be two common examples of commercially available solid-state products.

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