RAID disk array resolution

Raid,redundant Arrays of the abbreviation for independent disks, redundant array of independent disks, referred to as disk array.

The disk array is actually divided into soft array (Software RAID) and hard array (hardware RAID).

Soft array: That is, through software programs and the computer's CPU to provide operational capabilities. Because the software program is not a complete system, it can only provide the most basic RAID fault-tolerant functionality. Other such as hot standby hard drive settings, remote management and other functions are one by one to serve.

Hard array: The control and calculation capabilities of the entire disk array are provided by the hardware that is operated independently. Does not depend on the system's CPU resources. Because the hard array is a complete system, all the required functions can be done. Therefore, the hard array provides better function and performance than the soft array. The hard array is the only option if you want the system to do the same on the disk array. So we can see that the RAID Level 5 disk arrays on the market are hard arrays. Soft arrays are available only for RAID 0 and RAID 1.

There are two main ways to use disk RAID, the first of which is a RAID adapter card, which is plugged into a PCI slot and then connected to the hard drive to implement the raid feature of the hard disk. The second approach is to integrate the raid control chip directly on the motherboard to enable the motherboard to implement disk RAID directly. This approach costs a lot less than a dedicated RAID adapter card. Soft raid can also be made with a 2k or XP or Linux system. Personal use of disk raid is primarily done with RAID0, RAID1, or raid0+1 mode of operation

The following are the various levels of RAID described below.

RAID 0

Strip-band (stripe) storage, the data-stripping-strip technology. RAID 0 enables multiple hard drives to be connected to a larger hard drive cluster, improving disk performance and throughput. RAID 0 has no redundancy or bug fixes and is low cost, requiring at least two disks, typically used only if the data security requirements are not high. RAID 0 sequentially splits data in bits or bytes, reads/writes on multiple disks in parallel, and RAID 0 is the fastest at all levels. Theoretically, a RAID0 of n disks is n times the read and write speed of a single disk. But RAID 0 has no redundancy, and if one disk (physical) is corrupted, all of the data is unusable. So it's not really a RAID structure.

(1), RAID 0 simplest way

is to put n pieces of the same hard disk in the form of hardware by using a smart disk controller or using a disk driver in the operating system to cascade the software together, to form a separate logical drive, the capacity is n times the size of a single hard drive, which is written to each disk when the computer data is written, and when the space of a disk is exhausted, The data is automatically written to the next disk, and the advantage is that it can increase the capacity of the disk. Speed is the same as any one of the disks, if any one of the disks fails, the entire system will be destroyed, reliability is the use of a single hard drive 1/n.

(2), another way of RAID 0

is the use of N-block hard to choose a reasonable band size to create a stripe set, preferably for each hard disk is equipped with a dedicated disc controller, in the computer data reading and writing to the N-block disk reading and writing data, speed up n times. Improve the performance of the system.

RAID 1 has the following characteristics:

(1) Each disk of RAID 1 has a corresponding mirror disk, at any time the data is synchronized mirroring, and the system can read data from any disk in a set of mirrored disks.

(2), the disk can use only half the total disk capacity, the system cost is high.

(3), as long as there is at least one disk in any pair of mirrors in the system can be used, or even half a number of hard disk problems when the system can run correctly.

(4), the failure of the raid system is no longer reliable, should be timely replacement of the damaged hard disk, otherwise the remaining mirror disk also problems, then the entire system will collapse.

(5), replace the new disk after the original data will need a long time synchronous mirror, the external access to data will not be affected, only then the performance of the entire system has declined.

(6), RAID 1 disk controller load is quite large, with multiple disk controllers can improve the security and availability of data.