First, what does raid mean?
RAID is an abbreviation for "redundant Array of independent Disk", what does raid mean? Plainly speaking, the Chinese translation came to the popular point is the disk array meaning, that is, RAID is to make a hard disk array, and the array is the combination of hard disk configuration, as a general management, the most critical is that the array of disks with redundant fault-tolerant processing, This can improve the security and stability between the disk, there is no "single-point" hard disk phenomenon, it will not make some hard disk read and write frequently, the other hard disk may be less data exchange phenomenon, so as to improve the security of the disk, the same time the overall management of disks will improve the read and write speed, so that the use of the hard disk
Second, what does RAID5 mean?
We use different ways of doing disk arrays, and we call each disk array the level of RAID (that is, RAID levels). RAID5 is only one of the most common fault-tolerant methods in RAID levels. What does that RAID5 mean?
What do you mean, RAID5? Professional speaking:
The so-called RAID5 is the independent disk structure of distributed parity. RAID5 is the most extensive type of RAID level in the actual commercial application environment, after all, the development of computer technology to today, the quality of the hardware is relatively secure and stable, RAID5 the biggest feature is a hard disk redundancy, do RAID5 will need more than 3 pieces of hard disk, The usage rate is N-1 storage space. It is characterized by the existence of its parity code on all disks, RAID5 read efficiency is very high, write efficiency generally, block-type collective access to ask the efficiency is good. Because the parity code is on a different disk, it improves reliability by agreeing to a single disk error. RAID 5 is also a data check bit to ensure the security of data, but it is not a separate hard disk to hold the data check bit, but the data segment of the check bit interaction on each hard disk. This way, no matter what one hard drive is damaged, you can reconstruct the corrupted data based on the check digit on the other hard disk.
Three, RAID5 a few pieces of hard disk?
How many hard drives do RAID5? Simple to say: the so-called RAID5 is the use of more than 3 (including 3 hard drives) to do an array, of which two disk is the actual capacity, among which there is a disk as a spare, 3 disk agreed to a bad piece of disk, support online replacement, and data is not lost! 3 disk is the start, can be 4 blocks, 5 pieces, whether it is a few blocks, the actual capacity is (N-1).
Iv. How to do RAID5?
How do you actually do RAID5? Very easy, now whether it is hpserver, or ibmserver, there is a bootable CD or boot partition, follow the instructions step-by "next" can. However, it is important to note that different server, standard disk array RAID controller, supported RAID level is not the same, some of the standard machine does not have a RAID controller, and some with major raid functions, such as raid0,raid1,raid0+1, and does not support RAID5, For example, Blade server, supports up to two hard disk, can not do RAID5 at all, and basically support RAID5 function for normal server general high match!
Comment: RAID5 is actually a relatively economical level of fault tolerance, that is, the full use of the capacity of the hard disk, but also the redundancy of backup, of course, this and the budget has a relationship, such as 3 disk, then the hard disk utilization is 2/3, assuming that 8 disk, the utilization of up to 7/8! Now on the basis of RAID5, the redundant hard disk to find a disk to make a mirror (that is, RAID1) has produced a raid5+1 RAID6, RAID6 is actually RAID5 upgrade version, can agree to the same time bad two disk, without losing data! Such RAID6 level, also in the server hard disk more situation is used, do RAID6 generally is hard disk more than 5 to make sense, suppose is 4 block, RAID6 is actually RAID1 (N-2). So 4 disk do RAID6 significance, also did not do so!
Attention:
1, RAID1 heating is 3 disk but the capacity is a disk capacity and three disk to do RAID5 is two disk capacity 2, RAID5 in three block when bad two block probability is not large but more than 4 block 5 block when the probability is big, so add a hot-spare or is necessary. The concept of hot-standby is usually not to participate in the array, is an empty disk in the array of a piece of disk broken hot-standby to the top
RAID5 What do you mean? How do I raid5?raid5 a few hard drives?
