Learn about RAID
In the late 1980s and early 1990s, the information technology service providers faced with the rapid rise of a huge volume of data need to be stored. The storage technology is becoming very expensive to put a large number of high capacity hard drive on the server. RAID born to solve the problem above.
RAID is defined as? First of all RAID stands for Redundant Array of Inexpensive Disks (system disk backup). This system works by connecting a series of low-cost hard drives together to form a single large capacity storage device support efficient and reliable than the previous solution this. RAID is used and implemented methods in the enterprise storage and servers, but 5 years later RAID has become common for people to use.
The advantage of RAID
There are three main reasons for the application of RAID:
Provision
High efficiency
Low cost
The backup is the most important factor in the process of developing the RAID server environment. Backup allows the backup memory data if something goes wrong. If one drive in the array is a problem, then it can swap to another hard drive without shutting down the system or you can use the backup hard drive. Preventive methods depend on the version of RAID is used.
When applying the powerful RAID version you can clearly see its high efficiency. Efficiency also depends on the number of drives associated with each other and the control circuit.
All managers of the IT corporations want to reduce costs. When RAID born, price is a key issue. The objective of the RAID array is to provide better memory system compared to the separate use of high-capacity drives.
There are three levels of RAID used for desktop systems are RAID 0, RAID 1 and RAID 5. In many cases, only two of the three-level is effective and one of the techniques used is not a level of RAID.
RAID 0
RAID 0 is not actually a valid RAID level. Level 0 is given can not provide the level of redundancy for data storage. Thus, if a hard drive fails, data will endanger.
RAID 0 uses a technique called "striping". "Striping" split single data block as shown in the figure and spread them across the hard drive. The effect of striping is to increase the effectiveness of enforcement. Can write blocks of data simultaneously to two hard drives, compared to a hard drive as before.
Below is an example of the data has been written to the RAID 0 like. Each line in the graph represents a data block and each column represents a different hard drive. The numbers in the table represent the data blocks. Duplicate numbers indicate a data block is repeated.
Therefore, if all six blocks of data in the table combined into a single data file, you can read and write to your hard drive faster than reading on a drive. Each drive when operating in parallel with one another can only read 3 blocks of data when it needs to use a single drive to read all 6 volumes of data. The drawback of this technique is that if one drive fails, data will not work. Need to access all 6 new data block can read data but can only access 3 blocks.
Advantages:
Increase storage efficiency.
Not lose data storage.
Disadvantage:
No backup drive.
RAID 1
RAID 1 is the first real version. RAID provides data backup methods with simple techniques "mirroring" (mirror data). This technique needs two separate hard drives with the same capacity. A hard drive is active, the rest is hard drive backup. When data is written to the hard work, and it is also written to the backup drive.
This is an example of data that is written to RAID 1 How. Each line in the graph represents a data block and each column represents a different hard drive. The numbers in the table represent the data blocks. Duplicate numbers indicate a data block is repeated.
RAID 1 provides a complete data backup version to the system. If a disk crash, the remaining drive is still active. The drawback of this technique is the only RAID storage with the smallest capacity of the two drives if storage on two independent drives used.
Advantages:
Provides comprehensive data backup.
Disadvantage:
Storage capacity is only as large as the smallest drive capacity.
No performance increase enforcement.
Many downtime to change the hard work when there is a problem.
RAID 0 1
This is a combination of RAID that some manufacturers have made to include the interests of the two versions together. This combination applies only to systems with at least four hard drives. Techniques "mirroring" and "striping" combine to create effective prevention. The first set of the drive is enabled and the data will be divided, the second set will reflect these data to the second drive.
The following example shows the data is written to a RAID 0 1 How. Each line in the graph represents a data block and each column represents a different hard drive. The numbers in the table represent the data blocks. Duplicate numbers indicate a data block is repeated.
In this case, the block of data will be distributed across the drives and mirroring between two settings. Effective implementation of RAID 0 is increased because the hard drive only takes half the time compared to a single drive while maintaining redundancy. The main drawback of this method is the cost because it requires at least four hard drives.
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Advantages:
Increase effective enforcement.
Backup all data.
Disadvantage:
Require large number of drives.
The ability to access data halved.
RAID 10 or 1 +0
RAID 10 is similar to RAID 0 +1. Instead of sharing data between drives and mirroring them setting the first two drives are mirrored to each other. This is set up RAID cage. Two pairs of drive 1 and 2, 3 and 4 will mirror each other. Then they will be set to the range of data distribution.
Here is an example of data that is written to RAID 10 How. Each line in the graph represents a data block and each column represents a different hard drive. The numbers in the table represent the data blocks. Duplicate numbers indicate a data block is repeated.
Also set as RAID 0 +1, RAID 10 requires a minimum of 4 drives to implement their functions. However the data is protected by RAID 10 RAID 0 +1 a lot safer.
Advantages:
Increase effective enforcement.
Backup all data.
Disadvantage:
Require large number of drives.
The ability to access data halved.
RAID 5
RAID 5 most powerful desktop system. Typical of them is the need to have a hardware controller to manage the hard drive, but a range of computer operating systems can do this through the software. This method uses divide "parity" (parity) to maintain data redundancy. Requires at least three hard drives of equal productive to apply RAID 5.
"Parity" is a binary math compare two blocks of data with a 3rd data block based on the first two blocks. The simplest explanation is even and odd. If the sum of the two blocks is even, the number of data bits is even, if the sum of the two individual data block is the number of bits is odd. Therefore operations 0 +0 and 1 +1 are 0, 0 +1 or 1 +0 is equal to 1. Based on this binary operation, a drive in the array is a problem, then it will allow the bit to "parity" restore the data when the drive is replaced.
Here is an example of data that is written to RAID 5 How. Each line in the graph represents a data block and each column represents a different hard drive. The numbers in the table represent the data blocks. Duplicate numbers indicate a data block is repeated. "P" is the bit "parity" for two data blocks
The bit "parity" rotation between the drive will increase performance and data reliability. Range of hard drives will increase efficiency through a single drive because the drive is capable of writing data faster than a single drive. Data backup is also the whole by bit "parity". Where the second drive fails, the data can be recovered based on the data and the bit on the other two drives. The amount of data volume reduction is due to the parity data. In fact, if n is hard and z is the number of space, we have the following formula:
(N-1) * z = Size
In case 3 with 500GB hard drive / drives, the total capacity will be (3-1) x500GB = 1000 GB
Advantages:
Increase the storage capacity
Backup all data
Quick swap 24x7
Disadvantage:
High price
Implement effective reduction in the recovery process
RAID software and hardware
To use RAID functions, it is necessary to install software on the operating system or through dedicated hardware to control the flow of data from the computer to the hard drive. This is really important when RAID 5 is inherited large amounts of computer requirements to make the appropriate calculations.
For software, the cycle of the central processing unit (CPU) performs the tasks necessary for RAID. Using the software, the cost will be lower because all that is needed is the hard drive. The only problem with the RAID software is a decrease system performance. In general, the results can range from 5% or more depending on the processor, memory, hard drives and RAID types will be put to use. Many people no longer use the software RAID due to the price of the hardware RAID controller has decreased in recent years.
RAID hardware has the advantage of using a dedicated circuit to control all the calculations for external RAID processor. This method creates high-performance storage. RAID hardware problem is the price. Price for the controller RAID 0/1 is very small by many "chipset" was built on the motherboard. While hardware RAID 5, the request should have been added circuits.
Hard drive options
Many people are unaware that the power and capacity of a RAID array depends very much on the type of hard drive is used. To achieve the best results, all hard drives in the network should have the same style and brand. Besides, we also need to have the same size and same performance. There is no requirement for consistency between the drive but if the drive is not unified can affect RAID array.
The capacity of the RAID depending on their level. For RAID 0, division can be implemented through the space of two hard drives. 100GB with two 80GB drives and then the final production of the series will be 160GB. Similarly to RAID 1, the drive can only compare the data in the smallest size so that the final capacity will only be 80GB. RAID 5 is more complicated than when calculated by the formula above. If using 3 drives 80GB, 100GB and 120GB capacity is 160GB of data.
Execution time of the sequence depends on the hard drive. To perform a command function, you will have to wait for the data to be written to each drive before you can continue to the next step. This means that the graph example of the RAID array, the controller must wait until the data has been written to block 1 across all the drives in the array before you can continue other settings for the hard drive. Also means that in the series, but a hard drive performance only half will slow down the speed of the drive.
RAID installation
Installing RAID in general rely on the mainboard BIOS, RAID Controller and virtually no difficulties.
After plugging the hard drive into place RAID on motherboard (refer to the documentation accompanying the product), you enter the BIOS of the motherboard to enable the RAID controller and specify the relevant port (usually in the Integrated Peripherals) .
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After this operation, you will save and reboot the computer. Note carefully the message screen and press the right key combination when the computer is required (probably Ctrl + F or F4, depending on the RAID controller) to enter the RAID BIOS.
For RAID BIOS, though each with a different interface (refer to accompanying documents) but basically you have to perform the following actions:
+ Specifies the RAID drives will be involved.
+ Select RAID (0/1/0 +1 / 5).
+ Specify the Block Size: This is the key to a very large impact on the performance of the rig drives running RAID. For RAID Striping format, block size also means Stripe Size. If this parameter setting does not match the demand for it is a waste of memory and reduced performance. For example, if Block Size value is 64KB, 64KB minimum will be written to the drive in any case, even if it is a text file with a capacity of 2KB. So this value should roughly correspond to the average size of the file you are using. If the hard drive contains many small files eg Word document, you should to baby block size, the if containing more movies or music, large block size will give better performance (especially with RAID 0 system).
In addition, Block size is also a function of other decisions where the file will be written to. Return to 64KB Block Size example, if the file size is less than 64KB, it will only be written to a hard drive in RAID systems and so will not have any performance improvement. In another case, a file size of 150KB will be written to disk 3 with the 64KB + 64KB + 22KB and the controller can read the information from the three at the same time allow to accelerate significantly. If you select the block size is 128KB, the file will only be written to two hard 128KB + 22KB only. In fact, you should select the Block Size is 128KB for the desktop unless specific needs.
After the controller has perfect recognize the new drive system, you install the operating system as well as format the RAID drive. Windows XP is a smart choice.
Installing Windows in general the same as normal, but you need to prepare a floppy drive and a floppy disk containing the driver (driver) for the RAID controller. Immediately after pressing the keyboard to enter the installation, you must pay attention to the words the bottom of the Windows screen to press F6 in time. Then wait a while and when asked, you press S to bring the RAID driver to install.
The remaining steps, you manipulate just as with the normal installation on a hard disk.
After the system has stabilized, you pay attention to install the add-on RAID system controller to make use of the extensive features and sometimes even performance. You can list a number of programs such as the Intel Application Acceleration RAID Edition or nVIDIA RAID Manager ...
General Note:
If you have a drive full of data and want to set up RAID 0, you have to format the drive and do everything. So find yourself a suitable backup plan. If using RAID 1, this is not necessary.
Usually with a RAID 0 system you should have a small hard drive to store the most important things if you have problems, although very unlikely.
When the computer restarted (especially when abnormal boot), the system will stop for a long time in the process of RAID controller recognized the drive, maybe even more strange roar in the hard disk. You do not have to worry because this is perfectly normal controller to synchronize the operation of all drives in the RAID group that it manages.
RAID disk groups usually consist of several hard drives should work together significant heat is generated, there is no benefit in the long run. You find the cooling solutions if possible to avoid unwanted trouble.
conclusion
RAID support systems with many different utilities depending on the version of the application. Most customers will use RAID 0 option to increase the speed of implementation without reducing memory space. Mainly due to excess is not a major problem for the average user. In fact, most of the computer system only provides RAID 0 or RAID 1. The cost to implement RAID 0 +1 or RAID 5 is too expensive for the average customer and only applies to workstations or high-end server systems.
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