RAID Basics and Dmadm of Linux soft raid

Raid
0: Strip
Performance boost: Read, write n
Redundancy capability (fault tolerance): none
Space utilization: NS
At least 2 pieces of disk

1: Mirror
Performance improvement: Write performance decreased, read performance improved
Redundancy capability: Available
Space utilization: 1/2
At least 2 pieces of disk
2:
5 |
4:
3 |
Performance: Read and write promotion
Redundancy capability: Available
Space utilization: (n-1)/n
At least 3 pieces of disk

0+1 first, then do the mirror.
Performance: Read and write promotion
Redundancy capability: Available
Space utilization: 1/2
At least 4 pieces of disk

1+0 Mirror First, then do strip.
Performance: Read and write promotion
Redundancy capability: Available
Space utilization: 1/2
At least 4 pieces of disk

5+0
Performance: Read and write promotion
Redundancy capability: Available
Space utilization: (n-2)/n
At least 6 pieces of disk

JBOD: Increase capacity only, Hadoop distributed HDFS
Performance: No lift
Redundancy capability: None
Space utilization: 100%
At least 2 pieces of disk


Hardware RAID
Disk array Cabinets
Array cards
Motherboard array Chip

Software raid
Linux Soft raid:
Md:
Mdadm: Make any block device raid
Modal Commands:
To create a pattern:
-C
Dedicated options:
-L: Level
-N: Number of devices
-a <yes|no>: Automatically create a device file for it
-c:chunk size, data shard size, default 64KB
-X: Specify the number of free disks

# mdadm-c/dev/md0-a yes-l 0-n 3/dev/sd{b,c,d}-Create raid0/dev/md0 three-block disk

# mdadm-c/dev/md0-a yes-l 1-n 2-x 1/dev/sd{b,c,d}-Create RAID1 with free disk

# Cat/proc/mdstat-View array status
Management mode:
--add,--Remove,--fail
# mdadm/dev/md0--fail/dev/sdb---/dev/sdb to unavailable state
Monitor mode:
-F
Growth mode:
-G
Assembly mode:
-A

View details of a RAID array
# mdadm-d/dev/md0
--detail

Stop array:
# mdadm-s/dev/md0
--stop

Save current RAID information to a configuration file for later assembly
# mdadm-d--scan >/etc/mdadm.conf
# mdadm-a/dev/md0--assemble with saved mdadm.conf

RAID Basics and Dmadm of Linux soft raid