Note: The difference between raid0+1 and raid1+1

Today the company new server, OPS brother in the disk array, what raid, not before contact.

The following information from Baidu know:

In general, there are several categories of RAID: RAID0: The data is read and written by multiple hard drives concurrently, and the data is distributed evenly on each hard disk, in general, the more hard disks are used, the faster the reading and writing is done. RAID0 is characterized by fast read and write speed and low price; The disadvantage is that the security is relatively poor because the entire array of data will be lost in the event of a hard disk failure in RAID0. RAID0 is the fastest and most efficient type of disk array, but there is no fault-tolerant capability. RAID1: Called disk mirroring. The principle is to create a full image between two hard drives, which means that all data is stored on two physical hard disks, and when one disk fails, the data can still be read from another hard drive, so security is ensured. However, the cost of the system is greatly increased, because the system's actual effective hard disk space is only half of all hard disk space. RAID 0+1: The combination of RAID0 and RAID1, which is a mirror relationship of two identically configured RAID0, improves both the reading speed of the array and the security of the array data, and, of course, the cost is also expensive. RAID3: is to divide the data into multiple "blocks", according to a certain fault-tolerant algorithm, stored in the n+1 hard disk, the actual data occupied by the space of n hard disk sum, and the first n+1 hard disk stored on the data is to verify fault-tolerant information, when one of the hard drives in this n+1 a failure, Data from other n hard drives can also restore the original data, so that only using these n hard drives can also continue to work with injuries (such as capture and playback footage), when a new hard disk is replaced, the system can re-restore the full checksum fault-tolerant information. Because in a hard disk array, more than one hard disk at the same time the probability of failure rate is very small, so under normal circumstances, the use of RAID3, security can be guaranteed. Compared to RAID0, RAID3 is relatively slow in terms of reading and writing speed. The principle of RAID5:RAID5 and RAID3 is very similar, the effective use of hard disk space is the same, but its algorithm and data chunking different ways. Using the fault-tolerant algorithm and the size of the block to determine the use of RAID applications, under normal circumstances, RAID3 more suitable for large file types and high security requirements of the application, such as video editing, hard disk broadcast machine, large database, etc., and RAID5 suitable for smaller file applications, such as text, pictures, small database and so on.

RAID level          RAID0        RAID1         RAID3            RAID5
fault tolerance              No there are
redundant types            no          replication        Parity parity
Hot Backup Select No there is a
hard drive required        one or more even number of at least        three         at least three
Valid hard drive capacity full hard disk capacity 50% HDD capacity  n-1/n   

RAID 0+1 is divided into two parts of the disk, two parts of the respective stripe (from a logical point of view: multiple disks as a large hard disk), and then the two parts of the good image

RAID 1+0 is the grouping of disks into groups (N/2), with 2 fast disks in the group mirroring, and then all of the groups striped (that is, merging as a large hard disk)