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What is RAID?



The RAID System, Redundant Array of Independent Disks, allows the users to combine multiple hard drive to one anther. It was originally designed as a replacement to the more expensive SCSI hard drives. There are many RAID levels with each level having a different performance to reliability ratio.

RAID 0 (Stripping)- In here the two hard drives are grouped together to make it look like one large (the two hard drives storage are combined) hard drive in the operating system. Data is written alternately between the two drives, meaning that each hard drive contains different data. This setup good for performance but not for reliability. If any one of the hard drives fail then you are at loss, since no backup is made on the second hard drive.
RAID 1 (Mirroring)- In here the two hard drives are grouped together to make it look like one regular single hard drive in the operating system. In the this setup the operating system writes to only one hard drive and the RAID System reads from the first hard drive and rewrites the data on the second hard drive. This setup is good for reliability but not for performance.
RAID 10 (0+1)- In here both RAID 0 and RAID 1 principles are used. It stripes each of the hard drives for capacity and performance and then mirrors them on other drives. This setup generally requires four hard drives with two hard drives (they are stripped to make it look like one larger hard drive) mirroring the other two hard drives (these two are also stripped to make it look like one larger hard drive).
RAID 5-In here Only RAID 1 principles are used. In this setup each of the hard drives are stripped but instead of mirroring, additional information is written on this larger hard drive for data recovering purposes. Less space is taken up in this setup then that of mirroring. Thus, this setup is ideal if you want maximum storage. However, this setup will be less reliable then that of mirroring, since the additional information are dependent on each of the hard drives.







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