|
IT247’s quick and easy guide to RAID
What is RAID?
RAID stands for Redundant Array of Independent Disks. This is a method of writing data simultaneously over multiple disk drives. The idea is to combine standard hard drives into an array to perform much better than a single hard disk whilst your computer sees it as a standalone hard drive.
Why would I need RAID?
- For speed and capacity.
- If you need maximum redundancy (in the case of drive failure your data is still available)
- For an ideal combination of speed and security
- Increased read and write performance
What are the different level’s of RAID?
RAID Level 0 – (Also called striping). This offers superior read and write performance. The data is split into blocks and distributed simultaneously among 2 or more Hard Drives. So for example 2 Hard Drives of 500GB Capacity in RAID 0 are faster than a single 1TB hard drive. RAID 0 however does not offer any redundancy.
RAID Level 1 – (Also called Mirroring). This is used to make an exact copy of the data on one hard drive and copy to another. This RAID level offers only half the capacity of the hard drives used. For example if you have 2 x 1TB drives you will only have 1TB on useable storage since you will be making a copy on the other drive. The benefit to this is that you have complete redundancy, if one of the drives fail you will still have your valuable data.
RAID Level 1+0 - This requires a minimum of 4 drives and combines RAID 1 Mirroring with RAID 0 Striping. First the Hard Drive’s are mirrored then striped across the member disks. Again due to mirroring you loose half the capacity but do gain the peace of mind that comes with RAID 1 and the performance of RAID 0.
RAID Level 5 - (Also called Parity) This offers redundancy like RAID 1 but with more useable disk space. The minimum number of disks required is 3 and you will only loose the space of 1 hard drive. So if you have 4 x 1TB hard drives, under RAID 5 you will have 3TB’s of useable space. RAID 5 breaks your data into chunks, calculates parity, then stripes the data and parity across the disk drives. So for example if you have 4 hard drives at RAID level 5, your data will be split into 4 blocks, 3 of which would contain the data and the forth would be the parity block. Each block is then striped across the hard drives. The redundancy element is achieved by good old algebra! If A+B = C you only ever need to know the value of 2 of them to find out the third. The same principle is applied in RAID 5, so if one of the 4 drives fail you can rebuild the data because your RAID controller knows the values across the other three drives.
What products offer RAID?
|