LEARN ABOUT SOLID STATE DISKS
What is a solid state disk?
A Solid State Disk (SSD) is a storage device that uses memory chips to store data, as opposed to mechanical disk drives that store data on a rotating platter with a traveling read/write head.
How does it work?
Most SSDs appear to the host system as a standard disk drive, but employ some form of main memory such as RAM or flash memory to store data. The controller on the SSD does the work of translating disk commands into memory commands, as well as assuring data integrity and performance.
Why use a SSD?
In a word: SPEED!
The most common applications that benefit from SSD performance are:
- Operating systems
- Databases
- Internet cache for faster web surfing
- Audio and Video editing
- CAD programs
- Software compilers
- Speeding up CD/DVD encoding/duplication
- Games (load times)
- SETI processing
- TEMP files
- Swap space
- Web server cache
- OLTP servers
- Virtual servers
- Thin client servers
- Custom applications with high I/O, high bandwidth, or high security requirements
What kinds of SSDs are there?
SSDs come in 3 principal varieties:
Flash-based utility drives
These drives are used for consumer electronics and portable storage.
They are the USB thumb drives and CF cards used in MP3 players, phones, and digital cameras. They are typically physically small and have capacities from 64MB to several gigabytes.
Flash-based 2.5" and 3.5" disk form factor drives
These drives are used primarily in rugged applications. However, there is a market in 2.5" flash disks emerging for high-performance laptops. These drives will be used for power savings and speed, rather than for their rugged features. They range in capacity from 1GB to 155GB
RAM-based drives
These are drives designed for high-performance computing environments where fast access to data is key. They use RAM as the primary storage media for speed, but because RAM is volatile, they typically back up to a non-volatile media such as a disk. RAM-based SSDs can come in standard disk form factors as well as 19" rack-mounted systems. They range in capacity from 1GB to 128GB.
Currently, RAM-based drives have the smallest market share of the three types of SSDs. While they widely out-perform the other drive types, they are more costly, less dense, and often physically large and complicated.
Just how much faster is a SSD than a mechanical disk?
There are two primary performance metrics for storage: Throughput - Megabytes per second (sequential), and IOPS - Input/Output operations per second (random and sequential).
Throughput is most important for streaming applications and large data transfers, for example, video streaming or loading a large data file.
IOPS are most important for accessing small files and file fragments, for example, virus scanning, database searches and page files.
Below is a graphic showing the relative performance of a 7,200 RPM mechanical disk, a 15,000 RPM mechanical disk, a flash-based SSD, and a RAM-based SSD.
| Disk Type | Throughput | Random IOPS |
|---|---|---|
| 7,200 RPM | 60 MB/s | 100 |
| 15,000 RPM | 80 MB/s | 140 |
| Flash SSD | 30 MB/s | 1,000 |
| RAM SSD | 100+ MB/s | 40,000+ |
Will SSDs replace mechanical hard disks?
Not for a while. SSD's are just now low enough in cost per GB to become a viable alternative to mechanical disks for storing performance-sensitive data. The pricing of the raw memory per GB is at a point where SSDs are best used in tandem with mechanical disks.
Starting in 2007, it will become more and more common to see systems with both solid state and mechanical storage. Windows Vista has support for several features that allow RAM, flash, and mechanical disks to all be used together to create a high performance system without adding too much cost.
Links :
Wiki page on solid state disks
http://en.wikipedia.org/wiki/Solid_state_disk