linux-Software RAID

The disk array is made up of many inexpensive disks, combined into a large disk group, which uses individual disks to provide data with the added effect to improve the performance of the entire disk system. Using this technique, the data is cut into many sections and stored on each hard drive

The disk array can also take advantage of the concept of the same-bit inspection, in the array of any one hard disk failure, can still read the data, when the data is reconstructed, the data is calculated and re-placed into the new hard disk

RAID Grade	Minimum hard drive	Maximum fault tolerance	Usable capacity	Read Performance	Write Performance	Security	Purpose	Application Industry
Single Drive	Reference	0	1	1	1	No
JBOD	1	0	N	1	1	None (with raid 0)	Increase capacity	Personal (temporary) storage backup
0	2	0	N	N	N	One hard drive exception, all hard drives will be abnormal	The pursuit of maximum capacity, speed	Video Splicing Cache usage
1	2	N-1	1	N	1	The highest, a normal can	The pursuit of maximum security	Personal, Enterprise backup
5	3	1	N-1	N-1	N-1	High	The pursuit of maximum capacity, minimum budget	Personal, Enterprise backup
6	4	2	N-2	N-2	N-2	Security is higher than RAID 5	With RAID 5, but more secure	Personal, Enterprise backup
10	4	N/2	N/2	N	N/2	High safety	Comprehensive raid 0/1 advantages, faster theoretical speed	Large databases, servers

1. n represents the total number of drives

2. Jbod can be connected to an existing hard drive to increase capacity directly

3. If the hard drive to create the raid is large, it may take a while for Cat/proc/mdstat to see the progress

Create a good software RAID corresponding to/dev/mdn,n for digital

RAID information is saved in the/proc/mdstat file and can be viewed through the mdadm command

Mdadm

-C Create a new raid

-S off specify raid, uninstall before closing

-R re-enable specified RAID (requires restart)

-D View RAID information (Cat/proc/mdstat can also be viewed)

-a automatically create the corresponding device

-l Specifies the raid level

-N Number of drives

-x Specifies the backup disk-X followed by the number

-F indicates the hard drive is faulty

-R removing the hard drive

-A add a new hard drive to the raid

--ZERO-SUPERBLOCK/DEV/SDB Delete all information and data (RAID is off first)

Cases:

1. Create a RAID10 with a number of 4 drives

Mdadm-c/dev/md0-a yes-l 10-n 4/dev/sdb/dev/sdc/dev/sdd/dev/sde

2. Mount the file system after it is created

Mkfs.xfs-f/dev/md0

mount/dev/md0/home/

3. Set up auto mount on boot

Vim/etc/fstab

/dev/md0/home XFS Defaults 0 0

1. Batch create file test data is missing

Cd/home

Touch {1..20}

2. Mark SDB as the failed drive and remove

Mdadm/dev/md0-f/dev/sdb

Mdadm/dev/md0-r/dev/sdb

ll/home/See if data is missing

Add a piece of hard disk

Cat/proc/mdstat Discovery [4/3]

is rebuilding

Mdadm/dev/md0-a/dev/sdb

Cat/proc/mdstat

[=========>...] recovery = 45.9%

linux-Software RAID