By Justin Tanker
RAID data storage is a very commonly used technique for maintaining and accessing large amounts of information. Most RAID applications are used on computer servers, though there are some levels that can be used for desktop applications as well.
In this article we'll look at what exactly RAID is, what it does and the advantages and disadvantages of using this technology.
What is RAID?
RAID is an acronym for Redundant Array of Independent Disks. The technique was invented in the late 1980s and continues to be used today. In essence, RAID is a way for multiple disk drives to work together and present themselves to an operating system as a single data storage medium.
RAID has essentially three goals, to improve the performance capability of a computer or server, to increase the storage capacity of said computer and to improve the reliability of the data stored on it.
Different levels of RAID accomplish these three goals to a greater or lesser degree depending on the storage technique that is used.
RAID Techniques
RAID uses a couple of basic data storage techniques to achieve its goals. The three basic data storage techniques are mirroring, striping, and parity.
Mirroring is the process of making an identical copy of a set of data and storing it on more than one disk. This provides data redundancy, which protects your data by making it possible to retrieve the information from a different drive in your system if the original hard drive fails for some reason.
Striping is the process of allocating data among various drives in the system. Striping evenly distributes data on each of the drives which allows you to access the information more quickly.
Parity is a technique that allows you to reconstruct blocks of data in the event of a drive failure. Each level of RAID uses these techniques in different ways to achieve the common goal of increased capacity, speed and reliability.
RAID levels
There are many different levels of RAID. The levels differ in the way that they store and process data and are not to be considered sequential in performance ability. For example, RAID 5 is not necessarily better than RAID 1, nor is RAID 100 better than RAID 50. The most commonly used levels today are RAID 0, 1, 5 and 6 along with the nested levels 10, 50, 51 and 60. (We'll get to nested levels shortly).
There are seven standard levels of RAID, 0 through 6. Levels 2, 3 and 4 are now considered obsolete. In addition to these standard levels, there is quite a variety of non-standard and nested levels. Non standard configurations include levels such as 7, 5E, 5EE and other exotic combination's. Nested levels combine two of the standard levels to form the nested level.
For example, level 10 is a combination of levels 1 and 0. For practical purposes, the array is designed as two separate RAID 1 arrays that communicate with the system and each other as if they were individual drives in a RAID 0 array. This allows you to combine some of the advantages of level 1 with the advantages of level 0, producing a more powerful and flexible array.
Each level has its own strengths and weaknesses. As a general rule, RAID 0 has the best performance and data storage capability of any of the other arrays, however it provides no fault tolerance, so if any drive in the system fails for any reason, you would lose all of your data. For this reason, RAID 0 systems are often combined with other levels such as RAID 10, 50 or 60 to combine the performance advantages of RAID 0 with the data reliability of the other levels.
RAID 1 and 10 both provide high levels of performance and data reliability, but their storage capacity is relatively low. RAID 5 and 50 are great for reading data, but relatively slow in writing new data to the drives. It has excellent storage capacity and is a relatively inexpensive option compared to some of the other levels. RAID 5 tends to be the most popular RAID level available.
RAID 6 and 60 provide the best data protection ability and excellent read performance, though the write performance is relatively slow. RAID 60 tends to be among the most expensive of RAID options.
There is no one best RAID level for everyone. The best solution depends on your needs for storage capacity, data protection and performance in both reading and writing data to the drive.
If you're unsure as to what level is best for you, consult a your local computer service provider or data recovery specialist. Article Source: http://EzineArticles.com/?expert=Justin_Tanker |
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