RAID Calculator helps in RAID assistance. The tool calculates capacity, data protection, and unused space characteristics for RAID 0, RAID 1, RAID 5, RAID 6, RAID 10, RAID 50, and RAID 60.
The tool will help you calculate the fault tolerance characteristic in different RAID levels.
Following are minimum number of disks required be each Raid type:
In the past, mainframe computers used large and expensive hard disks designed to manage the data promptly. But that structure had a drawback if it failed; the overall system collapsed and would lose all the data unless you have the backup. Therefore, the expensive disk would need to be replaced.
Soon cheaper hard drives came into the market, but they were not reliable, with failure being all too common. So what was the solution?
RAID stands for Redundant Array of Inexpensive Disks or Redundant Array of Independent Disks. It's a logical way of arranging the disks together in an array, using many disks together, acting as one. The logic behind that structure is to use several cheap hard disks to get the speed and reliability of an expensive disk.
There are many ways to configure and arrange those inexpensive hard disks, depending upon the speed and reliability you want. But the exact speed and reliability you will get from RAID highly depend upon the RAID level you select.
1 - RAID 0 (Striping): In RAID 0, the data is broken into blocks and written alternately to each RAID hard disk. Suppose you have two disks, Disk 0 and Disk 1. The odd-numbered blocks will be written on Disk 0, and even-numbered blocks will be written on Disk 1. The process is called striping. The performance is doubled because reading and writing can happen simultaneously. An individual file can use the speed and capacity of all the disks of an array, resulting in a significant increase in performance as you are reading and writing from multiple disks at once.
But there is also a drawback, that RAID 0 is NOT redundant. If even one disk failed, you would lose all of your data.
RAID 0 is an excellent choice where you need high performance, and data exists somewhere else. For example, you can use this in a server environment for caching purposes, where you need fast speed, but data reliability or data loss is not a big issue.
2 - RAID 1 (Mirroring): In RAID 1, the data is mirrored on each hard disk, so suppose one disk fails, the second disk has the data backup. That RAID level is all about reliability and fault tolerance. However, in performance, RAID 1 is nowhere near RAID 0 as writing performance will be the same because writing the same data on both drives simultaneously. But the reading performance would be slow. However, as per theory, that would be the sum of the speed of two disks.
To maximize the performance, you will need to select the RAID hardware and software carefully. You will add more disks, but it will increase the cost per usable capacity. Suppose you have three mirrored disks; if two of your disks failed, you still have the last one to avoid data loss. However, the total usable space would only be a third of the entire capacity of all hard disks.
3 - RAID 5 (Distributed Parity): In RAID 5, the data is striped into several disks, like RAID 0. But to make it fault tolerance and redundant, a block of data called parity data is efficiently written on an extra hard disk.
In RAID 5, you require a minimum of three hard disks. Suppose one disk fails, you can recover the data by using the rebuilding process where the parity data is used to recover the lost data in conjunction with the remaining data.
However, rebuilding the RAID array requires a lot of time and severe sacrifice of performance. Once you replaced the failed disk, it will need a significant array's performance to rebuild the data from the parity information. It does not compare well with today's enormous hard disks and could take hours or days to complete. During the rebuilding operation, the array will be at risk of another disk failure, which would mean a total loss of data.
4 - RAID 6 (Dual Parity): RAID 6 is an extended version of RAID 5, where you use a second parity block means it includes double parity. That allows two disks to fail without any data loss. In RAID 6, you require a minimum of four hard disks. Suppose one disk fails, which causes the data to rebuild. If another disk fails, there is still no data loss. That means RAID 6 is twice the fault tolerance of RAID 5.
5 - RAID 10 (RAID 1+0): The RAID 10 uses the concept of mirroring and striping. In RAID 10, you require a minimum of four hard disks, the set, or two or more mirror disks striped together. That means RAID 10 allows a total of two disks failures, one per mirrored set.
6- RAID 50 (RAID 5+0): In RAID 50, several RAID 5 arrays are striped together. That means one disk per sub-array can fail without any data loss. In RAID 50, you require a minimum of six hard disks.
7 - RAID 60 (RAID 6+0): In RAID 60, several RAID 6 arrays are striped together. That means two disks per sub-array can fail without any data loss.
RAID 10, RAID 50, and RAID 60 are nested RAID levels. In RAID 60, you require a minimum of eight hard disks.
You require NO RAID when you can endure several hours of downtime and bear data loss while your site recovers from data backup.
RAID is beneficial when uptime and reliability are the essential metrics of your business. Backups are necessary because they help from severe data loss. But in any disk failure, restoring a large amount of data even takes several hours or days. RAID protects you from data loss without any downtime in case of failure of one or more disks.
However, you require RAID 0 when you need high performance and speed, and data loss or reliability is not essential for your business. On the other hand, RAID 1 provides you inexpensively gain, additional data redundancy, and read speeds.
RAID 5 or RAID 6 is essential when you have web servers, high read environments, or massive storage arrays as a single object. However, the RAID 10 is the most suitable one if you need fault tolerance but want fast rebuild time. It provides additional read and writes speed as well as additional redundancy.
Note: When referred to disk capacity, one gigabyte equals one billion bytes, and one terabyte equals one trillion bytes. However, your computer's operating system may use a different standard of measurement and displays lower capacity. In addition, some of the listed capacity may use for formatting and other functions and may not be available for data storage.