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RAID (redundant array of independent disks; originally redundant array of inexpensive disks) provides a way of storing the same data in different places on multiple hard disks. By placing data on multiple disks, input/output operations can overlap in a balanced way, improving performance.
Raid 0:
This configuration has striping but no redundancy of data. It offers the best performance but no fault-tolerance.
Raid 1:
Also known as disk mirroring, this configuration consists of at least two drives that duplicate the storage of data. There is no striping. Read performance is improved since either disk can be read at the same time. Write performance is the same as for single disk storage.
Raid 5:
This level is based on block-level striping with parity. The parity information is striped across each drive, allowing the array to function even if one drive were to fail. The array’s architecture allows read and write operations to span multiple drives. This results in performance that is usually better than that of a single drive, but not as high as that of a RAID 0 array. RAID 5 requires at least three disks, but it is often recommended to use at least five disks for performance reasons.
Raid 10:
Combining RAID 1 and RAID 0, this level is often referred to as RAID 10, which offers higher performance than RAID 1 but at a much higher cost. In RAID 1+0, the data is mirrored and the mirrors are striped.
this is raid-0 is one disk required no parity disk no fail over disk is failed data is gone.
Raid-1 is minimum two disk required parity one disk read and write fast accessible data.
raid-5 is minimum 3 disk required.two disk usable one disk parity.
Raid-10 is two disk required fast accessible data rebuilding fast synchronous.
RAID:-Redundent array of independent Disk
RAID0 -striping
RAID1-mirroring
RAID5-2+1 parity
RAID10-mirroring&striping
RAID is a way to store data in differnet places on disks in case of disk faliure.
RAID 0 --> store the data distributly between the 2 disks. so if you have 2T disks you get actualy 2T. if one disk fails you lose 0.5 of your data.
RAID 1 --> store the data into disk and copy it to another disk. so if you have 2T disks you get actualy 1T. if one disk fails you lose nothing.
RAID 5 --> store the data and the parity distributly between minimum 3 disks.so if you have 3T disks you get actualy 2T. if one disk fails you lose nothing.
RAID 10 --> you have 2 disks for the striped data and 1 for the parity.so if you have 3T disks you get actualy 2T. if one disk fails you lose nothing.
What is RAID, why do you need it, and what are all those mode numbers that are constantly bandied about? RAID stands for “Redundant Array of Independent Disks” or “Redundant Array of Inexpensive Disks,” depending on who you talk to. Note that the wordarray is included in the acronym, so saying “RAID array,” as a lot of people do, is redundant.
Back when hard drives were less capacious and more expensive, RAID was created to combine multiple, less-expensive drives into a single, higher-capacity and/or faster volume. On top of that, it was designed to facilitate redundancy, also known as fault tolerance or failover protection, so that the array and its data remain usable when a drive fails. You’ll often hear about 1-disk or 2-disk redundancy, which refers to the number of drives that can fail while the array remains viable.
Redundancy is important for a small business, as drive failure does happen. RAID’s data redundancy offers no protection against data lost to malware, theft, or natural disaster—and it’s certainly no substitute for proper backup practices—but it does provide a fail-safe against hardware failure.
RAID has levels, or methods by which the drives are ganged together; commonly people refer to levels by number. The three most common levels in the consumer and small-office markets are RAID 0, RAID 1, and RAID 5. However, you’ll encounter numerous other options too, including levels 6, 10, 5+1, JBOD (“just a bunch of disks”), and Microsoft’s virtual disk RAID, as well as abstracted RAID implementations such as Drobo BeyondRAID, Netgear X-RAID, and Synology SHR.
Common RAID ModesRAID 0 Picture the 0 in the “RAID 0” name as an oval racetrack and you’ve divined its primary purpose: Faster performance. RAID 0 distributes data across multiple drives (for example, block A goes to and from drive 1, block B goes to and from drive 2), which permits increased write and read speeds. This approach is often referred to as striping, and other modes (as you’ll see later) employ the technique as well.
Regrettably (and dangerously, if you aren’t aware of the risks) RAID 0 offers no protection against drive failure, since this mode does not write any duplicate or parity information. Hence, when a drive fails, you end up with a puzzle that’s missing pieces. In such a situation, your data is quite possibly gone, though you can find service providers that might be able to recover it—for a lot of money.
RAID 1 RAID 1 writes and reads the same data to pairs of drives; it’s also referred to asmirroring. The drives are equal partners—should either fail, you can continue working with the good one until you can replace the bad one. RAID 1 is the simplest, easiest method to create failover disk storage. However, it costs you a whopping 50 percent of your total available drive capacity; for example, two 1TB drives in a mirrored array nets you only 1TB of usable space, not 2TB.
You may have as many pairs of mirrored drives as your RAID controller allows. And in the unlikely event that said consumer-grade controller supports duplex reading, RAID 1 can provide an increase in read speeds by fetching blocks alternately from each drive.
RAID 5 This RAID mode offers both speed and data redundancy. RAID 5 writes data to and reads from multiple disks, and it distributes parity data across all the disks in the array. Parity data is a smaller amount of data derived mathematically from a larger set that can accurately describe that larger amount of data, and thus serves to restore it. Since parity information is distributed across all the drives, any drive can fail without causing the entire array to fail.
RAID 5 uses approximately one-third of the available disk capacity for parity information, and requires a minimum of three disks to implement. Since data is read from multiple disks, performance can improve under RAID 5, though some users report that RAID 5 slows performance greatly when it’s processing multiple reads in a server situation.
RAID stands for Redundant Array of Inexpensive (Independent) Disks.
On most situations you will be using one of the following four levels of RAIDs.
This article explains the main difference between these raid levels along with an easy to understand diagram.In all the diagrams mentioned below:
RAID 0 consists of striping, without mirroring or parity. The capacity of a RAID 0 volume is the sum of the capacities of the disks in the set.RAID 1 consists of data mirroring, without parity or striping. Data is written identically to two (or more) drives.RAID 5 consists of block-level striping with distributed parity so it requires at least three disks. A RAID 10 configuration requires a minimum of four disks, and stripes data across mirrored pairs. As long as one disk in each mirrored pair is functional, data can be retrieved
