RAID 0
This configuration is designed for speed and has no disk redundancy, which means that if one drive fails then you have lost your data. For certain business needs this may be preferable in situations where the data is not valuable but having it processed as fast as possible is more important.
RAID 0 uses disk striping (See last week’s blog for a definition) which is great for fast disk access as the files are being written across two disks.
PRO’s – fast data reading.
CON’s – no redundancy.

RAID1
This type of raid array is designed solely for redundancy purposes. The data is mirrored across drives so if one drive fails the other drive has identical data on it (See Mirroring in last week’s blog). This is a more common setup as most businesses require redundancy to protect their data. RAID 1 is not designed for speed and is slower than RAID0.
PRO’s – Disk redundancy.
CON’s – Slower reading and writing of data.

RAID5
This setup is designed with redundancy in mind and not speed. It is different to RAID1 in that the data is still striped and not mirrored. However there is one big difference between RAID0 and RAID5 and that is that RAID5 has disk parity.
What is Parity?
Disk parity is constructed by the RAID controller additionally to the user data and is constructed in such a way that if any of the user data is lost the RAID can reconstruct the data. The RAID controller keeps a value of the all the parts of the data added up.This way if one part is missing it can simply reconstruct that part by looking at the whole and subtracting the parts of the data that are present. The result is the missing data.

This means that your data is quite safe and the system also works fast as it uses disk striping and not disk mirroring.
PRO’s – Redundancy.
CON’s – Requires a minimum of 3 disks to setup and RAID 0 is faster.
RAID10
RAID10 combines both RAID0 and RAID1 to gain the best out of both configurations. This means that your disk array will have the speed and performance of RAID0 and the redundancy of RAID1. The problem with this configuration is that it requires a minimum of four disks and has no parity. However the fact that the arrays are mirrored means that parity is not required.

PRO’s – Excellent performance and redundancy.
CON’s – Expensive and can be complicated to set up if the RAID controller does not support RAID10.
There are other RAID setups however these are the most common and the others configurations are generally a combination or minor altering of these configurations.
In conclusion I would like to remind you that RAID setups are there to provide protection against disk failure and are not a substitute for having a backup system in place. Any data that is important needs to be and should be backed up regularly.