For the most part deffinitely hardware RAID. However, software RAID has some few advantages, but its beyond the scope of this FAQ to discuss this further. For further details on advantages/disadvantages of software RAID.
Cost: If you are already running an operating system that supports software RAID, you have no additional costs for controller hardware; you may need to add more system memory to the system, however.
Simplicity: You don’t have to install, configure or manage a hardware RAID controller.
Duplexing: Duplexed RAID 1 can sometimes be implemented in software RAID but not in hardware RAID, depending on the controller.
Performance: The best-known drawback of software RAID is that it provides lower overall system performance than hardware RAID. The reason is obvious: cycles are “stolen” from the CPU to manage the RAID array. In reality, this slowdown isn’t that excessive for simple RAID levels like RAID 1, but it can be substantial, particularly with any RAID levels that involve striping with parity (like RAID 5).
Boot Volume Limitations: Since the operating system has to be running to enable the array, this means the operating system cannot boot from the RAID array! This requires a separate, non-RAID partition to be created for the operating system, segmenting capacity, lowering performance further and slowing boot time.
Level Support: Software RAID is usually limited to RAID levels 0, 1 and 5. More “interesting” RAID levels require hardware RAID (with the exception of duplexing, mentioned above.)
Advanced Feature Support: Software RAID normally doesn’t include support for advanced features like hot spares and drive swapping, which improve availability.
Operating System Compatibility Issues: If you set up RAID using a particular operating system, only that operating system can generally access that array. If you use another operating system it will not be able to use the array. This creates problems with multiple-OS environments that hardware RAID avoids.
Software Compatibility Issues: Some software utilities may have conflicts with software RAID arrays; for example, some partitioning and formatting utilities. Again, hardware RAID is more “transparent” and may avoid these problems.
Reliability Concerns: Some RAID users avoid software RAID over concern with potential bugs that might compromise the integrity and reliability of the array. While hardware RAID controllers can certainly also have bugs, I think it’s reasonable to believe that some operating systems are more likely to have these sorts of problems than a good-quality hardware RAID controller would.
related reading:How to set up RAID drives and enhance hard disk performance/How to achieve drives raid/What is the difference between RAID 0 and RAID 5E.Software RAID/What Types of RAID Exists And The Difference.
