The LVM is a shorthand of logical volume management, initially developed by IBM, the purpose of designing to freely change the partition size to meet the user's disk capacity requirements. It allows the drive to span the disk, adjust the size of the drive, etc., such as file systems (such as EXT2), using the block devices provided by LVM instead of directly using hard drives. Simply put, the LVM adds a management layer in the middle of the partition used by the hard disk and the user, and the user can change the size of the partition accordingly by changing the size of the logical volume, without having to directly operate the hard disk. The benefits of doing this are - even if the size of the partition is changed, the data on the partition will not be lost. For specific methods, please see the LVM section in this topping.
RAID is a short written in the Redundant Array Of INEXPENSIVE / INDEPENDENT DISK. The most common way is to use PCI
The SCSI RAID controller (the array card), this is called hard RAID. Soft RAID can also be implemented under Linux, as long as Linux kernel support can be implemented, no need to buy expensive array cards, specific methods can look at the contents of the top. There is also possible to use SCSI-SCSI RAID. The role of RAID is used to achieve redundancy, backup, and improve hard disk read and write performance.
RAID 0 can increase the hard disk's read and write speed, which is only meaningful under hard RAID.
RAID 1 achieves two and more mirror images of two or more hard drives, and the mirroring is implemented with two and more than two partitions under soft RAID.
RAID 0 1 joins the advantages of the above two RAIDs, which requires both data redundancy to ensure the integrity of the data, and achieve distributed I / O to speed read and write speed.
RAID 3 provides parity on the basis of RAID 1, not much.
RAID 5 joins the advantages of RAID 0 1 and RAID 3, using parity data for redundant, and split the parity data on all disks, ease the bottleneck on parity disk. Commonly used. It is the best compromise between data availability and performance. At least three hard drives are required.
