I. What does RAID Mean?
Raid is the abbreviation of "Redundant Array of independent disk". What does RAID Mean? To put it bluntly, the Chinese translation means the disk array, that is to say, raid is to make the hard disk into an array, and the array is to combine and configure the hard disk, as a general management, the most important thing is that the disk of the array has redundancy and fault tolerance processing, which can improve the security and stability of the disk. There is no "Single Point" hard disk, that is to say, it will not make some hard disks read and write frequently, and other hard disks may have less data exchange, so as to improve the security of the hard disk. At the same time, the overall management of the disk will increase the read and write speed, maximize hard disk utilization.
2. What does RAID5 mean?
When we create a disk array, we use different methods. We call each disk array method a raid level (RAID levels ). RAID 5 is only the most common fault tolerance method among RAID levels. What does RAID5 mean?
What does RAID5 mean? Professional Lecture:
RAID5 is an independent disk structure of distributed parity. RAID5 is the most extensive raid level in the actual commercial application environment. After all, with the development of computer technology, the quality of hardware is quite reliable and stable, the biggest characteristic of RAID5 is that there is a Hard Disk redundancy, do RAID5 must be more than 3 hard disks, its usage is N-1 storage space. It is characterized by the existence of its parity code on all disks, RAID5 reading efficiency is very high, write efficiency is average, block-type collective question efficiency is good. Because the parity code is on different disks, the reliability is improved and an error occurs on a single disk. RAID 5 also ensures data security by the Data check bit, but it does not store the data check bit on a separate hard disk, but stores the check bit of the Data Segment on each hard disk. In this way, no matter what hard disk is damaged, the damaged data can be rebuilt based on the check bit on other hard disks.
3. How many hard disks does RAID5 have?
How many hard disks does RAID5 work? To put it simply: RAID5 is RAID 5, which uses more than three Disks (including three hard disks) as an array. The two disks are the actual capacity, and one of them is used as a backup, three disks agree to break one disk and support online replacement without data loss! 3 disk is the starting, can be 4, 5, whether it is a few, the actual capacity is (N-1 ).
4. How to Implement RAID5?
In fact, how to do RAID5? Very easy. Now, both hpserver and ibmserver have boot discs or boot partitions. Follow the instructions to "Next" step. However, you must note that raid controllers of different servers and standard disk arrays support different RAID levels. Some hosts do not have Raid controllers, while others do not have Raid functions, for example, raid0, raid1, and raid0 + 1 do not support RAID5. For example, a server with a blade can support a maximum of two hard disks and cannot implement RAID5; for general servers, the Advanced Configuration basically supports the RAID 5 function!
Comment: RAID5 is actually a fault-tolerant level that is more economical than swap, that is, the capacity of the hard disk that is fully utilized and the redundancy of backup. Of course, this is related to the budget, for example, three disks, the hard disk utilization rate is 2/3. If it is 8 disks, the utilization rate is as high as 7/8! Now, on the basis of RAID5, the redundant hard disk is used as an image (raid1), which generates the RAID5 + 1 raid 6 Statement. raid6 is actually an upgraded version of RAID5, I can agree to break two disks at the same time without losing data! This level of RAID 6 is also used when there are many server hard disks. it is meaningful to make raid 6 more than 5 hard disks, for example, four hard disks, raid6 is actually raid1 (N-2 ). Therefore, it is of little significance to use four disks for raid 6!
Note:
1. raid1 heating and backup are three disks, but the capacity is the capacity of one disk. RAID5 is the capacity of two disks. 2. RAID5 is broken when three disks are used. the probability is not big, but the probability is big when there are more than four or five blocks, therefore, it is necessary to add a hot backup. The concept of Hot Standby is that it usually does not crash with the array, that is, an empty disk is on top of an array when a hot standby disk breaks down.
