database raid

8/7/2019 database raid

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INTRODUCTION:

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RAID, an acronym forredundant array of inexpensive disks orredundant array of

independent disks, is a technology that provides increased storage reliability throughredundancy, combining multiple low-cost, less-reliable disk drives components into a logical

unit where all drives in the array are interdependent

Features of RAID

y Threaded rebuild process

y Fully kernel-based configuration

y Portability of arrays between Linux machines without reconstruction

y Back grounded array reconstruction using idle system resources

y Hot-swappable drive support

y Automatic CPU detection to take advantage of certain CPU optimizations.


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Advantages of RAID

The foremost advantage of using a RAID drive is that it increases the performance and reliabilityof the system. The RAID drive is a credible example that could be used in a server. The RAID

increases the parity check and thus it regularly checks for any possibility of a system crash. Disk

stripping is also a hot topic when we discuss about the RA

ID drives. The performance is muchhighlighting and increases a lot when the disk stripping is done. How the performance increasesa lot by the disk stripping? This is actually done by the interleaving of the bytes or the group of

bytes. The interleaving of this sort is done across the multiple drives. By this procedure only onedisk is reading or writing the data. The reading and writing of the data are done in a simultaneous

process.

The mirroring is the complete duplication of the data. Or in the other sense the mirroring is the100% duplication of the data on two drives. The drives may be considerably the RAID 1. Theconcept of parity comes after the concept and application of the mirroring. The parity involves

that the data from the crashed system be matched up with the data that is stored in the other disk.The parity check is the term allotted for the work it carries out. The procedure involved is done

as described below: the parity is used to calculate the data in the two drives and store the resultsin the third drive. In case there are more than two drives the parity check is done on all of them

and the results are stored on a completely altogether different drive. The preferable device maybe the RAID 3 or the RAID 5. And the failed drive is replaced.


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the drives into the RAID controller just like you would a SCSI controller, but then you add themto the RAID controller's configuration, and the operating system never knows the difference.

Software RAID

Software RAID implements the various RAID levels in the kernel disk (block device) code. It

also offers the cheapest possible solution: Expensive disk controller cards or hot-swapchassis [1]are not required, and software RAID works with cheaper IDE disks as well as SCSI

disks. With today's fast CPUs, software RAID performance can excel against hardware RAID.

The MD driver in the Linux kernel is an example of a RAID solution that is completely hardwareindependent. The performance of a software-based array is dependent on the server CPUperformance and load.

DIFFERENT LEVELS OF RAID AND LINEAR SUPPORT:

RAID LEVELS AND TYPES

RAID, an acronym ofRedundant Array of Independent (Inexpensive) Disks is the talk of theday. These are an array of disk to give more power, performance, fault tolerance and

accessibility to the data, as a single storage system. It's not mere combination of disks but all thedisks are combined providing standard MTBF (mean time before failure) reliability scheme;

otherwise chances are performance would be affected drastically if disks are not combined as asingle storage unit.

All the RAID types and models are commonly classified as RAID levels, since RAID

represented by a higher number is regarded to be superior, more efficient, high-performance

array than the low numbered RAID.

RAID 0 STRIPING


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It is the Stripped Disk Array with no fault tolerance and it requires at least 2 drives to be

implemented. Due to no redundancy feature, RAID 0 is considered to be the lowest rankedRAID level. Striped data mapping technique is implemented for high performance at low cost.

The I/O performance is also improved as it is loaded across many channels. Regeneration,

Rebuilding and functional redundancy are some salient features of RA

ID 0.

RAID 1 - Mirroring:

It is the Mirroring (Shadowing) Array meant to provide high performance. RAID 1 controller

is able to perform 2 separate parallel reads or writes per mirrored pair. It also requires at least 2drives to implement a non-redundant disk array. High level of availability, access and reliability

can be achieved by entry-level RAID 1 array. With full redundancy feature available, need ofreadability is almost negligible. Controller configurations and storage subsystem design is the

easiest and simplest amongst all RAID levels.

RAID 0+1:

It is the RAID array providing high data transference performance with at least 4 disks needed toimplement the RAID 0+1 level. It 's a unique combination of stripping and mirroring with all the

best features of RAID 0 and RAID 1 included such as fast data access and fault tolerance atsingle drive level. The multiple stripe segments have added high I/O rates to the RAID

performance and it is the best solution for maximum reliability.

RAID 3 works on the Parallel Transfer with Parity technique. The least number of disksrequired to implement the RAID array is 3 disks. In the RAID 3, data blocks are striped and

written on data drives and then the stripe parity is generated, saved and afterwards used to verifythe disk reads. Read and write data transfer rate is very high in RAID 3 array and disk failure

causes insignificant effects on the overall performance of the RAID.

RAID 4:

RAID 4 requires a minimum of 3 drives to be implemented. It is composed of independent disks

with shared parity to protect the data. Data transaction rate for Read is exceptionally high andhighly aggregated. Similarly, the low ratio of parity disks to data disks indicates high efficiency.

RAID 5:

RAIDS 5 is Independent Distributed parity blockof data disks with a minimum requirement


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of at least 3 drives to be implemented and N-1 array capacity. It helps in reducing the writeinherence found in RAID 4. RAID 5 array offers highest data transaction Read rate, medium data

transaction Write rate and good cumulative transfer rate.

RAID 6:

RAIDS 6 is Independent Data Disk array with Independent Distributed parity. It is knownto be an extension of RAID level 5 with extra fault tolerance and distributed parity scheme

added. RAID 6 is the best available RAID array for mission critical applications and data storageneeds, though the controller design is very complex and overheads are extremely high.

RAID 7:RAID 7 is the Optimized Asynchrony array for high I/O and data transfer rates and isconsidered to be the most manageable RAID controller available. The overall write performance

is also known to be 50% to 90% better and improved than the single spindle array levels with noextra data transference required for parity handling. RAID 7 is registered as a standard trademark

of Storage Computer Corporation.

RAID 10:

RAID 10 is classified as the futuristic RAID controller with extremely high Reliability andperformance embedded in a single RAID controller. The minimum requirement to form a RAID

level 10 controller is 4 data disks. The implementation of RAID 10 is based on a striped array ofRAID 1 array segments, with almost the same fault tolerance level as RAID 1. RAID 10

controllers and arrays are suitable for uncompromising availability and extremely highthroughput required systems and environment.

With all the significant RAID levels discussed here briefly, another important point to add is that

whichever level of RAID is used regular and consistent data backup maintenance using tapestorage is must as the regular tape storage is best media to recover from lost data scene

Linear RAID :

Linear RAID is a simple grouping of drives to create a larger virtual drive. In linear RAID, the chunks areallocated sequentially from one member drive, going to the next drive only when the first is completelyfilled. This grouping provides no performance benefit, as it is unlikely that any I/O operations will be splitbetween member drives. Linear RAID also offers no redundancy, and in fact decreases reliability -- if anyone member drive fails, the entire array cannot be used. The capacity is total of all member disks.


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CONCLUSION

RAID technology can be difficult to understand, especially for the beginner. Do go through theabove tips to understand it so that you can make better purchase decisions when building your

next computer system.


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