There are many different RAID array levels and each level has tasks for which it is most suited. The RAID level you choose for your system depends on the amount of storage you require, the way you need to access your data and other outside factors such as cost, preferences and other considerations.
The most common RAID configurations are levels 0, 1 and 5. There are also various combinations of these levels such as RAID 10 or RAID 50. Each level carries certain advantages and disadvantages depending on how you plan to use it.
Most Common RAID Levels
RAID 0 divides a set of data evenly among multiple hard drives, usually two drives. The main goal and benefit of using RAID 0 is improved speed/performance. With this level, there is no redundancy of data, that is, each individual batch of data is stored on only one disk. This makes RAID 0 systems vulnerable to data loss, since the failure of one disk on the array affects the entire system. The data is “striped” across both hard drives so none of the data on the failed disks can be recovered without a repairing a failed disk.
This leads to the unfortunate fact that the more hard drives you have in a RAID 0 configuration, the less you should rely on it. The more drives you have, the greater the chance that one of them will fail and the data on that drive will be lost, affecting the rest of the data as well.
Another result of this set up is that the storage capacity of the array is limited to the storage capacity of the smallest drive in the configuration.
RAID 1, on the other hand, stores an exact copy of your data on two or more drives. This makes your data much more secure; if one drive in the system fails, your data can simply be retrieved from any other drive in the system. This is known as data redundancy. With your files copied and stored on every drive in a RAID 1 system, you'd have to have all the drives fail simultaneously to lose all of your data.
Another significant difference between RAID 1 and RAID 0 is that with RAID 1, the reliability of the system increases with each drive used in the configuration. The more drives you use, the more copies there are of your data and the less likely that all drives will fail at the same time, causing the loss of your data.
The downside of the mirroring RAID 1 is that in certain situations if one drive fails or you accidently delete a portion of your data the other hard drive will mirror the damaged one.
RAID 5 offers the advantages of data storage redundancy along with a high level of performance. It works differently from RAID 0 and 1, using striping (distributing small segments of data across a number of hard drives) and parity (a technique that allows data to be reconstructed from any drive in the system if it is lost).
The combination of striping and parity adds a high degree of fault tolerance to your system, meaning that it can still function effectively even in the face of multiple drive failures. Your data is copied and spread out among all the hard drives in the configuration, so the chance of experiencing a complete system failure eliminating all your files is much lower.
If an individual drive fails on a RAID 5 system, the system continues to run as normal, and notifies the system administrator that the drive in question needs to be replaced. If you do find yourself in this position, it's important to replace the faulty drive as soon as possible to maintain the integrity and performance of the system. Failure to replace the damaged drive and allow an additional hard drive to go offline will result in major data loss. At this point a professional data recovery service should be utilized.
No matter which level of RAID array you use, if you do experience a system failure, your best option for retrieving your files is to contact a data recovery professional who has the tools, knowledge and experience to repair your damaged hard drives and recover your files.