Linux Base raid

Raid:

Redundant Arrays of Inexpensive Disks

Independent

Berkeley:a Case for redundent Arrays of inexpensive Disks RAID

Improved IO capability:

Parallel disk read and write;

Increased durability;

Disk redundancy to achieve

Level: Multiple disk organizations work together in different ways;

How the raid is implemented:

External disk array: Adapter capability with expansion cards

On-chip RAID: Motherboard integrated RAID controller

Software RAID:

Levels: Level

raid-0:0, strip reel, strip;

RAID-1:1, mirrored volume, mirror;

RAID-2

..

RAID-5:

RAID-6

RAID10

RAID01

RAID-0:

Read and write performance improvement;

Free space: n*min (S1,s2,...)

No fault-tolerant capability

Minimum number of disks: 2,

RAID-1:

Read performance improvement, write performance slightly decreased;

Free space: 1*min (S1,s2,...)

Have redundancy capability

Minimum number of disks: 2,

RAID-4:

1101, 0110, 1011

RAID-5:

Improved read and write performance

Free space: (N-1) *min (s1,s2,...)

Fault tolerance: 1 disks

Minimum number of disks: 3,

RAID-6:

Improved read and write performance

Free space: (N-2) *min (s1,s2,...)

Fault Tolerance: 2 disks

Minimum number of disks: 4, 4+

Mixed type

RAID-10:

Improved read and write performance

Free space: n*min (S1,s2,...) /2

Fault tolerance: Each group of images can only be broken one piece;

Minimum number of disks: 4, 4+

RAID-01:

RAID-50, RAID7

Jbod:just a Bunch of Disks

Function: The space of multiple disks is combined with a large continuous space;

Free space: sum (s1,s2,...)

Common levels: RAID-0, RAID-1, RAID-5, RAID-10, RAID-50, JBOD

Implementation method:

How to implement Hardware

How to implement Software

Implementation of software RAID on CentOS 6:

Combined with MD (multi devices) in the kernel

Mdadm: a modular tool

Syntax format for commands: mdadm [mode] <raiddevice> [options] <component-devices>

Supported RAID levels: LINEAR, RAID0, RAID1, RAID4, RAID5, RAID6, RAID10;

Mode:

Create:-C

Assembly:-A

Monitoring:-F

Management:-F,-R,-a

<raiddevice>:/dev/md#

<component-devices>: any block device

-C: Create pattern

-N #: Create this raid with # blocks of devices;

-L #: Indicates the level of RAID to be created;

-A {Yes|no}: Automatically create device files for target RAID devices;

-C Chunk_size: Indicates the block size;

-X #: Indicates the number of free disks;

For example: Create a RAID5 of 10G free space;

-D: Displays details of the raid;

Mdadm-d/dev/md#

Management mode:

-F: flag specifies that the disk is damaged;

-A: Adding disks

-R: Remove disk

Observe the status of MD:

Cat/proc/mdstat

To stop the MD device:

Mdadm-s/dev/md#

Watch command:

-N #: Refresh interval, unit is seconds;

watch-n# ' COMMAND '

Exercise 1: Create an RAID1 device with free space of 10G, request its chunk size is 128k, file system is EXT4, have a free disk, boot can automatically mount to/backup directory;

Exercise 2: Create an RAID10 device with free space of 10G, request its chunk size is 256k, file system is EXT4, boot can be mounted automatically to/mydata directory;

Blog job: RAID level features;

Linux Base raid