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Huaqiang Security Network News ]
Before introducing the important specification parameters of the disk array, the concept of the disk array is introduced. The so-called Redundant Arrays of Independent Disks (RAID) has the meaning of "redundant array of independent disks".
Disk arrays are made up of a number of cheaper disks that are combined into a large disk group. The effect of using individual disks to provide data increases the overall disk system performance. Using this technology, the data is cut into a number of segments, which are stored on separate hard disks. [1]
The disk array can also take advantage of the concept of Parity Check. When any hard disk in the array fails, the data can still be read. When the data is reconstructed, the data is calculated and re-inserted into the new hard disk.
Disk array important specification parameters
RAID 0: RAID 0 continuously divides data in bits or bytes and reads/writes on multiple disks in parallel. Therefore, it has a high data transfer rate, but it has no data redundancy, so it is not a true RAID structure. . RAID 0 simply improves performance and does not guarantee data reliability, and one of the disk failures will affect all data. Therefore, RAID 0 cannot be used in applications where data security is high.
RAID 1: It implements data redundancy through disk data mirroring, generating mutual backups on pairs of independent disks.
data. When raw data is busy, data can be read directly from the mirror copy, so RAID 1 can improve read performance. RAID 1 is the highest unit cost of a disk array, but provides high data security and availability. When a disk fails, the system can automatically switch to the mirror disk for reading and writing without reorganizing the failed data.
RAID 01/10: According to the combination of RAID 10 and RAID 01, it is actually a product of combining RAID 0 and RAID 1 standards, while continuously dividing data in units of bits or bytes and reading/writing multiple disks in parallel. , for each disk as a disk mirror for redundancy. Its advantage is that it has the extraordinary speed of RAID 0 and the high reliability of RAID 1, but the CPU usage is also higher, and the disk utilization is relatively low. RAID 1+0 is mirrored and re-partitioned data, and then all hard disks are divided into two groups, which are regarded as the lowest combination of RAID 0, and then these two groups are regarded as RAID 1 operations. RAID 0+1 is the opposite of RAID 1+0. It is to partition and then mirror the data to two sets of hard disks. It divides all the hard disks into two groups, which becomes the lowest combination of RAID 1, and treats each of the two sets of hard disks as RA.
ID 0 works. Performance, RAID 0+1 has a faster read and write speed than RAID 1+0. Reliability, when one hard disk of RAID 1+0 is damaged, the other three hard disks will continue to operate. RAID 0+1 As long as one hard disk is damaged, the other hard disk of the same RAID 0 will stop working, leaving only two hard disks to operate with low reliability. Therefore, RAID 10 is much more common than RAID 01. Most retail motherboards support RAID 0/1/5/10, but RAID 01 is not supported.
RAID 2: Blocks data on different hard disks, in blocks or bytes, and uses an encoding technique called "weighted average error correction code (Hamming code)" to provide error checking and recovery.
RAID 3: It is very similar to RAID 2 in that it distributes data across different hard disks. The difference is that RAID 3 uses simple parity and uses a single disk to store parity information. If a disk fails, the parity disk and other data disks can be heavy
New data generation; if the parity disk fails, it does not affect data usage. RAID 3 provides a good transfer rate for a large amount of continuous data, but for random data, the parity disk becomes a bottleneck for write operations.
RAID 4: RAID 4 also blocks data and distributes it on different disks, but the block units are blocks or records. RAID 4 uses a disk as the parity disk. Each write operation requires access to the parity disk. In this case, the parity disk becomes the bottleneck of the write operation, so RAID 4 is rarely used in commercial environments.
RAID 5: RAID 5 does not specify a parity disk, but instead accesses data and parity information across all disks. On RAID 5, the read/write pointer can operate on array devices simultaneously, providing higher data traffic. RAID 5 is better suited for small blocks of data and random reads and writes. The main difference between RAID 3 and RAID 5 is that RAID 3 needs to involve all the array disks for each data transfer. For RAID 5, most data transfers operate on only one disk and can be parallelized. operating. There is a "write loss" in RAID 5, that is, each write operation will produce four actual read/write operations, two of which read old data and parity information, and two write new data and parity information.
RAID 6: Compared to RAID 5, RAID 6 adds a second independent parity block. Two independent parity systems use different algorithms, and the reliability of the data is very high. Even if two disks fail at the same time, the data usage will not be affected. However, RAID 6 needs to allocate more disk space for parity information, which has a larger "write loss" than RAID 5, so the "write performance" is very poor. Poor performance and complex implementations make RAID 6 rarely practical.
RAID 7: This is a new RAID standard with an intelligent real-time operating system and software tools for storage management that can be run completely independent of the host and does not consume host CPU resources. RAID 7 can be seen as a storage computer (Storage Computer), which is significantly different from other RAID standards. In addition to the above various standards (such as Table 1), we can build a RAID array as required by RAID 0+1 in combination with multiple RAID specifications. For example, RAID 5+3 (RAID 53) is a widely used array. form. Users can generally configure disk arrays to obtain more suitable disk storage systems.
RAID 5E (RAID 5 Enhancement): RAID 5E is an improvement based on RAID 5 level. Similar to RAID 5, data verification information is evenly distributed on each hard disk. However, some unused ones are reserved on each hard disk. Space, this part of the space is not striped, allowing up to two physical hard drives to fail. It seems that RAID 5E and RAID 5 add a hot spare disk. It seems that RAID 5E distributes data on all hard disks, and performance is better than RAID5 plus a hot spare disk. When a hard disk fails, the data on the failed hard disk is compressed to the unused space on the other hard disk, and the logical disk maintains the RAID 5 level.
RAID 5EE: Compared to RAID 5E, RAID 5EE data distribution is more efficient. A portion of each hard disk is used as a distributed hot spare. They are part of the array. When one physical hard disk in the array fails, the data The speed of reconstruction will be faster.
RAID 50: RAID50 is a combination of RAID5 and RAID0. This configuration performs stripping of data including parity information on each disk of the RAID 5 subdisk group. Three hard disks are required for each RAID5 subdisk group. RAID 50 is more fault tolerant because it allows one disk in a group to fail without data loss. Moreover, since the parity bit is divided on the RAID5 subdisk group, the reconstruction speed is greatly improved. Advantages: Higher fault tolerance and the potential for faster data read rates. It is important to note that disk failures can affect throughput. The time to rebuild the information after the failure is longer than in the case of the mirror configuration.
Reverse osmosis water treatment agents are suitable for aromatic polyamide reverse osmosis membranes, hollow fiber membranes, and nanofiltration (NF) and ultrafiltration (UF). Excellent cleaning results can extend membrane run time.
Use the cleaning device to clean the system online. The steps are as follows:
1. The system is cleaned by reverse osmosis demineralized water for 3-5 minutes;
2. Check the cleaning tank, hose and precision filter and install a new filter if necessary.
3. Calculate the amount of cleaning drugs according to the system and membrane arrangement.
4. Inject the reverse osmosis water or demineralized water into the cleaning tank to the appropriate amount.
5. Slowly add the calculated dosing amount.
6. Adjust the pH of the solution to 2.0 using ammonia (NH3) or Hyde Energy HY-430.
7. Circulate and wash for 30 minutes under water pressure of 0.1Mpa (soaking effect will be better after soaking for 30 minutes); the cleaning flow rate should be recommended by the membrane manufacturer or system supplier.
8. If the pollution is serious, please drain the first return water (up to 15% by volume) to prevent redeposition of the pollutants.
9. If the cleaning solution becomes cloudy or the pH value exceeds the specified range, it is necessary to reconstitute the cleaning solution;
10. During the cleaning process, the pollutants will consume the cleaning chemicals, the PH value will change accordingly, and the cleaning ability of the medicine will be reduced. Therefore, it is necessary to monitor the change of pH value at any time and adjust the PH value in time.
11. Soak the membrane element in the cleaning solution, which is a very effective way to dissolve metal dirt. It is recommended to repeatedly soak and alternate the circulation of the water.
12. For multi-stage systems, each section should be cleaned separately for maximum effect.
13. Before the system is cleaned and re-commissioned, flush the system with low pressure until no more cleaning liquid remains in the system.
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