Disk arrays also utilize the concept of parity checking, whereby any one of the array's hard drives can still be read when the array fails.

There are usually 2 solutions for hard RAID

1 external storage enclosure (for general enterprise big data applications)

2 array card (for individual users or small data)

3 other cases, motherboard comes with RAID (usually not used for stability is not guaranteed)

Commonly used civilian NAS is usually soft RAID

The RAID is a combination of the following: Advanced RAID (for the first time in the history of the NAS) and RAID (for the second time in the history of the NAS). p>

RAID from 0 to 7***8 and RAID10 and RAID01

is to spread the continuous data access to multiple disks, so that the system data request can be executed by multiple disks in parallel, and each disk performs its own part of the data request. This parallel operation of data can fully utilize the bandwidth of the bus and significantly improve the overall access performance of the disks.

RAID 0 is not a true RAID structure, there is no data sink, no disk array with data checksums. RAID 0 requires at least two hard disks to implement, and it combines two or more disks into one, with data continuously split across each disk. Because the bandwidth is doubled, the read/write speeds are doubled, but while RAID 0 improves performance, it does not provide data protection, and all data will be lost if any of the disks are damaged. Therefore, RAID 0 should not be used in critical areas where high data availability is required.

There is no requirement for the number of disks, and disk utilization is 100% (limited to the smallest disk). No hot spare disks are required. All disks work together.

Reads and writes are limited to the slowest drive*N. Capacity is limited to the smallest disk*N

RAID1 is a RAID array of two hard disks with capacity equal to the capacity of only one disk because the other is only used as a "mirror" of the data. RAID 1 arrays are clearly the most reliable type of array because it is the most efficient way to store data. RAID 1 disk array is obviously the most reliable kind of array, because it always maintains a complete data backup. Naturally, it doesn't perform as well as a RAID 0 array, but it does read data faster than a single hard drive because the data is read from the faster of the two drives.

2 hard drives as a group, the data backup each other, disk utilization for a minimum of only 50%. There is no need for a hot spare disk.

Writes are limited to the slowest drive. Reads are limited to the fastest drive. Capacity is limited to the smallest disk

More than RAID0, there is a checksum disk, checksum disk damage data can not be recovered. It's not secure, it's not fast, and it's not highly utilized

RAID 5 is a storage solution that balances storage performance, data security, and storage costs. RAID 5 can be interpreted as a compromise between RAID 0 and RAID 1. RAID 5 can provide data security for the system, but the level of security is lower than Mirror and the utilization of disk space is higher than Mirror. RAID 5 has a similar read speed as RAID 0, but with an additional parity information, the write speed is slightly slower than writing to a single disk. RAID 5 has similar data read speed as RAID 0, except for the extra parity information.

RAID is the checksum and data are stored separately in the so disk, when a hard disk is damaged, the data in other disks with checksum data can be recovered from the damaged hard disk data. (Replacing the hard drive to rebuild the RAID or replace it with a hot spare disk). This is to avoid the damage of the verification disk leading to data unrecoverable situation.

RAID5 can continue to verify and store data even if one of the hard disks is damaged, so you need to replace the damaged disk in a timely manner (rebuild the RAID) to avoid overloading the remaining disks, which can cause more damage to the hard disks.

If the second disk is damaged, it is very difficult to recover the data.

RAID5 reconfiguration is very prone to failure, and multiple reconfigurations can cause disk damage.

The inherent flaw of high-capacity disks is that they have an Unrecoverable Read Error (URE) about once every 12TB of data, and if a URE occurs when reconfiguring a RAID, the system thinks there is an error on the disk, and the reconfiguration fails. So RAID5 will have multiple reconfiguration failures, increasing the load on the normal use of the hard disk and causing hard disk damage.

RAID6 technology is a RAID method designed to further enhance data protection on the basis of RAID 5, which is actually an extended RAID 5 level. The difference between RAID 5 and RAID 6 is that in addition to the XOR parity area for each hard disk, there is also an XOR parity area for each block of data. Of course, the current disk data block parity data can not exist in the current disk but interleaved storage, the specific form of the figure. In this way, each data block has two checksum protection barriers (a hierarchical checksum and an overall checksum), so the data redundancy performance of RAID 6 is quite good. However, because of the additional checksum, the write efficiency is worse than RAID 5, and the design of the control system is more complex, and the second checksum area reduces the effective storage space.

At least 4 hard drives as a group, the disk utilization rate of N-2. Because of the two validation CPC overhead is very large, disk read and write is not RAID 5 block

Can allow two hard disk colleagues damage (after replacement data can be recovered). The data is safer. This greatly reduces the risk of high-capacity hard disk in the later stages of use

There are patents that require a fee (skipped)

raid01 is more lack of security and difficult to recover from failures, almost no one will choose it in practice. The underlying RAID0 boosts the speed of the last RAID1 mutual backups (which were skipped)

RAID 1+0, also known as the RAID 10 standard, is actually a combination of the RAID 1 and RAID 0 standards, which continuously splits the data in bits or bytes and reads/writes multiple disks in parallel, while mirroring each disk for redundancy. Its advantage is that it has both the extraordinary speed of RAID 0 and the high data reliability of RAID 1, but the CPU occupancy rate is also higher, and the utilization rate of the disk is relatively low. Due to the utilization of RAID 0's extremely high read/write efficiency and RAID 1's high data protection and recovery ability, RAID 10 has become a cost-effective level, and almost all RAID controllers now support this level. However, the utilization rate of storage capacity of RAID 10 is as low as that of RAID 1, which is only 50%. Therefore, RAID 10 that is, high reliability and high efficiency disk structure it is a bandwidth structure plus a mirror structure, can achieve both high-speed and security purposes, RAID 10 can provide better performance than RAID 5. The scalability of this new structure is not good, this solution is widely used, the use of this solution is more expensive.

Fast reconfiguration, high security, 50% disk utilization Combined with the features of RAID 1-0

JBOD (just a bunch of disks, or sometimes called simple drive bundling) is a less formal term, officially called "spanning". JBOD (just a bunch of disks, or sometimes called simple drive bundle) is a less formal term, officially known as "spanning", which is used to refer to computer hard disks that have not been configured for RAID (Redundant Array of Independent Disks) systems to increase fault tolerance and improve data access performance.

RAID systems redundantly store the same data on multiple disks that appear to the operating system as a single disk. While JBOD also makes multiple disks appear to be one, it does so by combining multiple drives into one large logical disk. jBOD's use of separate disks doesn't provide any benefits, and doesn't provide any of the fault-tolerance or better performance, etc., that RAID does.

In JBOs mode, data is stored from the first hard disk all the way back, and the system can only see the large partition that contains all the hard disks, not the individual hard disks. The first hard drive is the system disk and if it is damaged, the data cannot be read. The storage mode is a single disk storage, do not store the hard disk in an idle state. (Single Disk Mode)

Depending on the number and capacity of disks? Automatically select which RAID mode to use

Convenient for those who are not familiar with RAID. Hard disk data can only be read on Qunhui.