Multiple Hard-Drives: which version of RAID?

There are now a number of manufacturers offering multiple hard drives in their notebooks. As a consequence, RAID in its various forms is becoming more popular. The question then becomes, "which version is right for me?" Ultimately the answer to that question depends on what you are going to use the computer for and how many disks your system will have...

Below I've compiled a short summary of the features of the more common forms of RAID that I found helpful when considering the subject. I 'borrowed' it from Wikipedia ( http://en.wikipedia.org/wiki/RAID), but there are many sites out there that discuss this topic.

RAID 0 and 5 tend to be the most common versions offered for notebooks. But of course you don't have to use RAID with multiple hard-disks at all. In this case, the OS will show multiple drives as such, e.g. C: & E: Others might wish to suggest which version of RAID they prefer and in what circumstances, e.g. gamer, business, general useage.

I hope you get something out of this thread

"RAID combines physical hard disks into a single logical unit by using either special hardware or software. Hardware solutions often are designed to present themselves to the attached system as a single hard drive, and the operating system is unaware of the technical workings. Software solutions are typically implemented in the operating system, and again would present the RAID drive as a single drive to applications.

There are three key concepts in RAID: mirroring, the copying of data to more than one disk; striping, the splitting of data across more than one disk; and error correction, where redundant data is stored to allow problems to be detected and possibly fixed (known as fault tolerance). Different RAID levels use one or more of these techniques, depending on the system requirements. A quick summary of the most commonly used RAID levels:

RAID 0
Striped set (minimum 2 disks) without parity. Provides improved performance and additional storage but no fault tolerance. Any disk failure destroys the array, which becomes more likely with more disks in the array. A single disk failure destroys the entire array because when data is written to a RAID 0 drive, the data is broken into fragments. The number of fragments is dictated by the number of disks in the drive. The fragments are written to their respective disks simultaneously on the same sector. This allows smaller sections of the entire chunk of data to be read off the drive in parallel, giving this type of arrangement huge bandwidth. When one sector on one of the disks fails, however, the corresponding sector on every other disk is rendered useless because part of the data is now corrupted. RAID 0 does not implement error checking so any error is unrecoverable. More disks in the array means higher bandwidth, but greater risk of data loss.

RAID 1
Mirrored set (minimum 2 disks) without parity. Provides fault tolerance from disk errors and single disk failure. Increased read performance occurs when using a multi-threaded operating system that supports split seeks, very small performance reduction when writing. Array continues to operate so long as at least one drive is functioning.

RAID 3 and RAID 4
Striped set (minimum 3 disks) with dedicated parity. This mechanism provides an improved performance and fault tolerance similar to RAID 5, but with a dedicated parity disk rather than rotated parity stripes. The single disk is a bottle-neck for writing since every write requires updating the parity data. One minor benefit is the dedicated parity disk allows the parity drive to fail and operation will continue without parity or performance penalty.

RAID 5
Striped set (minimum 3 disks) with distributed parity. Distributed parity requires all but one drive to be present to operate; drive failure requires replacement, but the array is not destroyed by a single drive failure. Upon drive failure, any subsequent reads can be calculated from the distributed parity such that the drive failure is masked from the end user. The array will have data loss in the event of a second drive failure and is vulnerable until the data that was on the failed drive is rebuilt onto a replacement drive."