HP RM435i Internal Black optical disc drive

RM435i DVD-ROM Drive, Software-based RAID & Hardware-based RAID HP supports both software-based and hardware-based RAID.
For example, HP now implements software RAID in embedded SATA controllers in some of the ProLiant servers and RBSU is used to enable it.

Software-based RAID

It is possible to have a RAID configuration without an array controller. This is known as software RAID.
With software-based RAID, the array management functions are implemented by software executing in a host environment such as the operating system.
Software RAID requires additional transfers across the I/O bus.
Although software RAID is not as versatile as hardware RAID, it offers a cost-effective, entry-level, fault-tolerant solution.
The advantages of software-based RAID are:
- The ability to span multiple host controllers (duplexing)
- Lower cost

Hardware-based RAID

With hardware-based RAID, the array management functions are implemented by the hardware and firmware within a RAID controller. The RAID controller orchestrates read and write activities in the same way a controller for a single disk drive does, treating the array as if it were a single physical or logical drive.

Hardware-based RAID is transparent to the host software and is self-contained within the storage solution. It does not interfere with the primary function of the host, which translates into higher overall performance and a potential for advanced RAID capabilities.

With a hardware RAID solution, there is no extra activity on the I/O bus, memory bus, or frontside bus after the data reaches the array controller. All RAID-related activities are local to the array SCSI bus. When a single sector is written to the disk, 64 transfers are executed on a 64-bit PCI bus.

The advantages of hardware-based RAID are:
- Faster, more reliable performance than software RAID
- Support for RAID 1+0 or RAID ADG
- Support for online spare drives
- Decreased processor load
- User-friendly configuration utilities
- No operating system interface required when starting a rebuild

Advantages of HP hardware-based RAID

HP implements RAID at the hardware level with value-added features in its Smart Array controllers. The advantages of HP hardware-based RAID are:
- Safe write caching through a battery-backed array accelerator on some models
- Superior manageability such as multiple volumes with different RAID levels
- High flexibility such as separating I/O in to different disk volumes
- Automatic recovery and online spares
- Automatic data distribution and I/O balancing across multiple disk drives
- Superior performance and I/O optimization