RAID 0
This is straight data stripping. It offers no data security and is used where maximum performance is the
only concern.
RAID 1
This is pure duplication. This is the most expensive back up because 2 times the number of disks is
needed than the amount of data to be stored. This offers no performance gains, but has the best
security.
RAID 2
This scheme hasn't been introduced, and probably never will. What it calls for is the addition of
additional ECC information to the data disks in a parity situation, so that data will likely be able to be
recovered if up to two disks are faulty for larger arrays.
RAID 3
This is straight parity. There is no performance gain, but it is an economical security against a single
hard drive failure.
RAID 4
This is parity based like RAID 3 and uses a dedicated drive, but the data is stored so that each of the
data disks can be accessed independently without the pariy disk speed bottlenecking their read and
write speeds as much. This is not used as much as RAID 3 is.
RAID 5
This RAID level uses parity information for data security, but doesn't store it on a separate disk. Parity
information is stored on each of the hard drives so that no extra parity hard drive is needed. This offers
the security against a single hard disk crash, with minimum performance loss compared to RAID 3 and
RAID 4.
RAID 6
A parity based approach like RAID 5, except for only one disk used for parity information, this scheme
uses two. This means that if both the 2 main disks are faulty, there is enough information to recover all
of the data. This isn't a great approach, and RAID 1 offers significantly more speed at the same
reliability level, so that this is RAID level is hardly ever used.
RAID 10 and RAID 1+0
This is simply the use of both RAID 1 duplication and RAID 0 stiping. It offers both the performance
gains of the striping and the redundant security of duplication. The simplest setup is 4 hard drives,
grouped into identical pairs.
RAID 30 and RAID 3+0
This is simply a RAID 3 configuration, except all of the data disks are further striped with data.
Because the parity is calculated before the data is stripped, if one of the RAID 0 disk configurations
fail, data is still recoverable.
RAID 50 and RAID 5+0
This is simply a RAID 5 configuration, except all of the data disks are further striped with data.
Because the parity is calculated before the data is stripped, if one of the RAID 0 disk configurations
fail, data is still recoverable.
