RAID
What is RAID
RAID: Redundant Arrays of Inexpensive (Independent) Disks Inexpensive (Independent) Disks
1988 by the University of California-Berkeley (University of California-Berkeley) "A Case for Redundant Arrays of Inexpensive Disks", multiple disks combined into a "array "To provide better performance, redundancy, or both
RAID function realization
- Improve IO capability, disk parallel read and write
- Improve durability, disk redundancy algorithm to achieve
RAID implementation
- External disk array: provide adaptability through expansion card
- Internal RAID: The motherboard integrates a RAID controller and is configured in the BIOS before installing the OS
- Software RAID: realized by OS, for example: Synology NAS
RAID level
Level: How multiple disks work together is different
RAID-0: Striped volume, strip
RAID-1: Mirrored volume, mirror
RAID-2
..
RAID-5
RAID-6
RAID-10
RAID-01
RAID level
RAID-0
Read and write data in chunk units
Read and write performance improvement
Available space: N * min (S1, S2, ...)
No fault tolerance
Minimum number of disks: 2, 2+
RAID-1
Read performance is improved, write performance is slightly reduced
Available space: 1 * min (S1, S2, ...)
has redundancy capability
Minimum number of disks: 2, 2N
RAID-4
The XOR calculation values of multiple data disks are stored in a dedicated check disk.
Disk utilization (N-1) / N
has redundancy capability.
At least 3 hard disks can be achieved.
RAID-5
Read and write performance improvement
Available space: (N-1) * min (S1, S2, ...)
has fault tolerance: allows up to 1 disk to be damaged
Minimum number of disks: 3, 3+
RAID-6
Read and write performance improvement
Available space: (N-2) * min (S1, S2, ...)
has fault tolerance: allows up to 2 disks to be damaged
Minimum number of disks: 4, 4+
RAID-10
Read and write performance improvement
Available space: N * min (S1, S2, ...) / 2
is fault-tolerant: each group of mirrors can only break one piece at
least The minimum number of disks: 4, 4+
RAID-01
Multiple disks first achieve RAID0, and then combined into RAID1
RAID-50
Multiple disks implement RAID5 first, and then combine to RAID0
Common levels:
RAID-0, RAID-1, RAID-5, RAID-10, RAID-50