What is a hardware-based RAID? RAID Data Recovery.

What is a hardware-based RAID?

A RAID is considered hardware-based when it is implemented in hardware, either on the motherboard directly or a separate RAID card. Windows views the entire RAID as a single disk. The individual component disks are controlled by the RAID controller and not directly accessible to Windows.

RAID (redundant array of independent disks) levels 0, 1, 3, and 5 are the levels typically implemented in hardware-based solutions.

Hardware-based RAID uses an intelligent drive controller and a redundant array of disk drives to protect against data loss in the event of media failure and to improve the performance of read/write operations. A disk array is an effective disk-storage solution for computers running database software.

Hardware-based RAID levels 1 through 5 automate redundancy and fault tolerance at the hardware level. All levels (0 through 5) incur no overhead on the system processor. Individual data files are typically spread across more than one disk. It is possible to implement a hardware-based RAID solution that provides your system with seamless, nonstop recovery from media failure.

In general, hardware-based RAID offers performance advantages over Microsoft Windows NT or Windows 2000 software-based RAID. For example, you can improve data throughput significantly by implementing RAID 5 through hardware that does not use system software resources. This is accomplished by using more disks at a given capacity than in conventional storage solution. Read/write performance and total storage size can be further improved by using multiple controllers.

Depending on the configuration, hardware-based RAID generally provides good performance. It also makes it much easier to manage multiple disks, allowing you to treat an array of disks as one disk. You may even be able to replace a failed drive without shutting down the system. The disadvantages of a hardware-based solution are cost, and it may lock you into a single vendor.

For more information about implementing hardware-based RAID, contact the hardware vendor.

	Description	Advantages
Software-based RAID	Primarily used with entry-level servers, software-based arrays rely on a standard host adapter and execute all I/O commands and mathematically intensive RAID algorithms in the host server CPU. This can slow system performance by increasing host PCI bus traffic, CPU utilization, and CPU interrupts. Some NOSs such as NetWare and Windows NT include embedded RAID software. The chief advantage of this embedded RAID software has been its lower cost compared to higher-priced RAID alternatives. However, this advantage is disappearing with the advent of lower-cost, bus-based array adapters.	Low price Only requires a standard controller.
Hardware-based RAID	Unlike software-based arrays, bus-based array adapters/controllers plug into a host bus slot [typically a 133 MByte (MB)/sec PCI bus] and offload some or all of the I/O commands and RAID operations to one or more secondary processors. Originally used only with mid- to high-end servers due to cost, lower-cost bus-based array adapters are now available specifically for entry-level server network applications. In addition to offering the fault-tolerant benefits of RAID, bus-based array adapters/controllers perform connectivity functions that are similar to standard host adapters. By residing directly on a host PCI bus, they provide the highest performance of all array types. Bus-based arrays also deliver more robust fault-tolerant features than embedded NOS RAID software. As newer, high-end technologies such as Fibre Channel become readily available, the performance advantage of bus-based arrays compared to external array controller solutions may diminish.	Data protection and performance benefits of RAID More robust fault-tolerant features and increased performance versus software-based RAID.
External Hardware RAID Card	Intelligent external array controllers "bridge" between one or more server I/O interfaces and single- or multiple-device channels. These controllers feature an on-board microprocessor, which provides high performance and handles functions such as executing RAID software code and supporting data caching. External array controllers offer complete operating system independence, the highest availability, and the ability to scale storage to extraordinarily large capacities (up to a terabyte and beyond). These controllers are usually installed in networks of stand alone Intel-based and UNIX-based servers as well as clustered server environments.	OS independent Build super high-capacity storage systems for high-end servers