UPDATE – Hardware v. Software RAID

This content was originally featured on Amdmb.com and has been converted to PC Perspective’s website. Some color changes and flaws may appear.

There are pros and cons to both hardware and software based RAID. Hardware-based RAID offers CPU independent performance, while software-based RAID can scale with the CPU to new performance levels. RAID systems are available at all price points, with software-based RAID offering a low-cost entry point for those who can not afford a traditional hardware RAID solution. The fact that software RAID uses the host CPU and host memory means that as CPU speed increases, and memory size and bandwidth increase, the throughput of a software RAID system also increases. In contrast, the throughput of a hardware RAID system is statically tied to the hardware RAID card, so the only way to increase RAID performance is to buy a newer hardware RAID card. In addition, software RAID can adopt new storage speeds much faster than hardware RAID. With the new Ultra160 SCSI products that are being released, SCSI bandwidth has reached all-time highs. A typical hardware RAID solution must be redesigned to integrate the new parts, while software RAID is already prepared to run on the new parts.

It is a commonly assumed that hardware RAID is more reliable than software RAID. However, both rely on RAID software to implement the RAID configuration. The only difference is that with hardware RAID the software runs on the RAID board, with software RAID the software runs on the main CPU. Both pieces of software are equally susceptible to failure due to bugs in the code, so the issue of reliability really does not involve where the code runs, but how well the code was written. This is where the reputation of the RAID vendor is important. Poorly written hardware RAID code, called firmware, is as likely to cause a failure as poorly written software RAID code. While RAID code that is well written can greatly enhance system reliability, whether it is a hardware or software RAID system.

Lastly, Software RAID solutions are significantly less expensive than hardware RAID solutions. The software RAID solutions that are bundled with an operating system are “free”, since they do come with the operating system. However, the adage that “you get what you pay for” is very true in software RAID. Third party RAID solutions do cost some money (typically less than hardware RAID solutions), but they increase system reliability immensely.

The test system:

Asus A7V
AMD 1000MHz processor
256MB Mushkin PC-150 Memory
Creative Labs 64MB GeForce Ultra
2-Seagate X15 Hard Drives
ATTO ExpressPCI RAID Kit
Adaptec 2100S RAID controller
Windows2000 Professional
32KB Block Size

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