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Residual information is also ored for the data in this disk array. The redundancy information consists of direct parity (parity) and parity information calculated based on various data blocks (RAID 4 or RAID 5). When RAID is used, the operating system (Windows *, NetWare *, or Unix) is interested in the same disk array that it sees as a single logical drive, rather than dealing with individual disks.

The main purpose of RAID arrays is to improve data availability and security. RAID prevents the system from going off when there is a hard drive failure, but it can not recover data that has been deleted by the user or damaged by an important event such as theft or fire. For this reason, after installing a RAID system, you must back up your data regularly to ensure that your system is protected against such problems.

There are two ways to put a RAID solution into practice. The hardware-based RAID controller is a smart component and can handle all RAID information on its own. If you set up such a system, the RAID controller takes over the entire control load of the RAID array instead of the host. The other method is to use a RAID solution that includes a RAID driver and a simple host adapter. In such systems, the drive is integrated with the operating system (for example, Windows * NT). Therefore, the performance of the RAID system is entirely dependent on the processing load of the host CPU, and you may experience problems recreating the array after a disk failure.

When choosing a hardware RAID RAID controller, you should be aware of the following points: ease of installation and maintenance, management software features, and the manufacturer’s experience in developing RAID components. Supporting the most important RAID levels (0, 1, 4, 5, 10) of the RAID controller should be able to handle arrays running on multiple channels and different RAID levels at the same time.

RAID Levels – How to edit drives

Each RAID level distributes the data in a different format to the drives in the row and is optimized for certain situations. This document discusses the most common RAID levels used today.

Detecting your RAID level

RAID 0

At this RAID level, two or more hard drives are combined to share manageable blocks (ABCD … in yellow cylinders) from the user. These blocks are distributed by striping to different drives in the RAID 0 array. As a result, two or more hard drives are combined and better read / write performance can be achieved, especially for sequential access. However, redundancy information is not stored in the RAID 0 array. In other words, if one of the hard disks fails, all the data is lost. A 0 in the RAID level indicates that this level does not contain redundancy. This is usually why RAID 0 is not used on servers where safety is important.

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Advantage: Provides the highest transfer rate
Disadvantage: If a disk fails because there is no redundancy, all the data is lost
Uses: Usually used in workstations to store temporary data and to achieve high I / O rate

RAID 1

In RAID 1 systems, the same data is stored on two hard disks (100% redundancy). When one of the disks fails, immediate use is offered without affecting the performance of the other disk drive system or the integrity of the data. When two disk drives are mirrored over a SCSI channel, this is called “Disk Mirroring”. If each of the disk drives is connected to a different SCSI channel, it is called “Disk Duplication” (provides additional security). RAID 1 is an easy and highly effective solution for data security and availability.

Advantage: High availability, Logical Drive with data can be used even if a disk fails
Disadvantage: Requires 2 disks, but only one can use the storage capacity
Uses: Used in small systems and boot disks where a diskin capacity is usually sufficient
Raid Configurations. What is Raid 0, Raid 1, Raid 4, Raid 5, Raid 10? How ?

RAID 4

RAID 4 is similar to RAID 0 in large measure. The data is distributed to the disk drives by the taping method. In addition, the redundancy information stored on another disk drive (P1, P2, …) is calculated via the RAID controller. Even if one of the disks fails, all the data is available. Missing data are calculated with the help of available data and accompanying information. Unlike RAID 1, only one disk drive’s capacity is used for redundancy. For example, in a RAID 4 disk array with 5 disk drives, 80% of the installed disk drive capacity is used as user capacity and only 20% is allocated for redundancy. If there are numerous small data blocks in the system, the accompanying disk can cause a bottleneck in terms of job production. In situations where large data blocks are used, RAID 4 provides a significant performance boost.

Advantage: High availability, Logical Drive with data can be used even if a disk fails
Advantage: Allows you to use the disk capacity very well (n-1 disk is used for storing data in a discrete array)
Disadvantage: Write performance is limited because it is necessary to calculate redundancy information
Uses: It is often used in large systems for data storage because of the very good ratio of installed capacity to available capacity

Raid Configurations. What is Raid 0, Raid 1, Raid 4, Raid 5, Raid 10? How ?

RAID 5

The parity information in the RAID 5 disk array is distributed to all disk drives, unlike the RAID 4 array. The RAID 5 disk array allows you to achieve a more balanced job production. It provides a very good response time, even for small blocks of data that are common in many users’ environments where multitasking is used. The security level of RAID 5 is the same as RAID 4: even if one of the disks fails, all the data is available. Missing data are recalculated with the help of available data and accompanying information.

Advantage: High availability, Logical Drive with data can be used even if a disk fails
Advantage: Allows you to use the disk capacity very well (n-1 disk is used for storing data in a discrete array)
Disadvantage: Write performance is limited because it is necessary to calculate redundancy information
Uses: It is often used in large systems for data storage because of the very good ratio of installed capacity to available capacity

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RAID 10

RAID 10 is the combination of RAID 0 (Performance) and RAID 1 (Data Security). Unlike RAID 4 and RAID 5, parity information does not need to be computed. RAID 10 disk arrays provide good performance and data security. As with RAID 0, the best performance is achieved in sequential loads. Similar to RAID 1, 50% of the installed capacity is spent for redundancy.

Advantage: High availability, Logical Drive with data can be used even if a disk fails
Advantage: Good write performance
Disadvantage: Requires at least four disks, and only half of this capacity can be used
Field of application: Typically used in environments where sequential write performance should be high

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