RAID (disk array) use

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 technology, the data is cut into many sections, stored on each hard drive, even if there is a piece of damage, no data loss, and can continue to use.

Introduction to RAID (disk array):

What is raid: multiple disks synthesize an "array" to provide better performance, redundancy, or both;

Features of 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: Provides adaptive capability through expansion cards;

Internal raid: Motherboard integrated RAID controller;

Configured in the BIOS before installing the OS;

Software RAID:

RAID level:

RAID-0: Striped Roll, strip

RAID-1: Mirrored volume, mirror

RAID-2

..

RAID-5

RAID-6

RAID-10

RAID-01

Introduction to RAID levels:

RAID-0:

Read and write performance improvement;

Free space: n*min (S1,s2,...) ；

No fault-tolerant ability;

Minimum number of disks: 2, 2;

RAID-1:

Read performance improvement, write performance slightly decreased;

Free space: 1*min (S1,s2,...) ；

have redundancy capability;

Minimum number of disks: 2, 2N;

RAID-4:

Multiple data disk XOR or operation value, stored in a special check disk;

RAID-5:

Read and write performance improvement;

Free space: (N-1) *min (s1,s2,...) ；

Fault tolerance: Allow up to 1 blocks of disk damage;

Minimum number of disks: 3;

RAID-6:

Read and write performance improvement;

Free space: (N-2) *min (s1,s2,...) ；

Fault tolerance: Allow up to 2 blocks of disk damage;

Minimum number of disks: 4, 4+;

RAID-10:

Read and write performance improvement;

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: Can be understood as an independent storage computer, with its own operating system and management tools, can run independently, theoretically the highest performance of the RAID mode;

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;

Soft RAID implementations:

MDADM: Provides management interface for soft raid;

Add redundancy to the spare disk;

Combined with the MD (Multi devices) in the kernel;

RAID devices can be named/dev/md0,/dev/md1,/DEV/MD2,/dev/md3, and so on;

Implementation of software RAID:

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 pattern:-C

-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;

Display mode:-D (displays RAID details)

Mdadm-d/dev/md#

Management mode:-F,-R,-a

-F: flag specifies that the disk is corrupt

-A: Adding disks

-R: Remove disk

Assembly:-A

Monitoring:-F

<raiddevice>:/dev/md#

<component-devices>: any block device

Observe the status of MD:

Cat/proc/mdstat

To stop the MD device:

Mdadm-s/dev/md#

Soft RAID Management:

Build configuration file: Mdadm–d–s >>/etc/mdadm.conf

Stop service: mdadm–s/dev/md0

Activation: mdadm–a–s/dev/md0

Delete Raid information: MDADM–ZERO-SUPERBLOCK/DEV/SDB1

Soft RAID Testing and remediation:

Analog disk failure:

#mdadm/dev/md0-f/dev/sda1

To remove a disk:

#mdadm/dev/md0–r/dev/sda1

To repair a disk failure from a software RAID disk:

Replace the failed disk and turn it on;

Rebuilding partitions on the standby drive;

#mdadm/dev/md0-a/dev/sda1

Mdadm,/proc/mdstat, and system log information

To implement a software RAID instance:

1. fdisk t FD (disk or partition conversion RAID format)

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2. Create a RAID device

Mdadm-c/dev/md0-a yes-l 5-n 4-x1/dev/sd{b2,c1,c2,d1,d2}1 (consent to create RAID device md0-l is RAID level,-N uses several blocks to make raid,-x spare blocks)

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Mdadm-d/dev/md0 (show created RAID)

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3. MKFS.EXT4/DEV/MD0 (Create file system for MD0)

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4. Vim/etc/fstab (edit config file)

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5. mdadm-ds/dev/md0 >/etc/mdadm.conf Generate configuration file

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6, start raid

Mdadm-a/dev/md0

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7, test

Mdadm/dev/md0-f/DEV/SDB2 Analog Damage

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Mdadm/dev/md0-r/DEV/SDB2 Deleting members

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Mdadm/dev/md0-a/DEV/SDF1 Increase

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Mdadm-g/dev/md0-n 6-a/dev/sdd4 added members

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7. Delete raid

Umount/mnt/raid (un-mount)

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Mdadm-s/dev/md0 Stop raid

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Rm-f/etc/mdadm.conf (delete config file)

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Vi/etc/fstab (Delete the edited profile)

FDISK/DEV/SDA (delete member of RAID)

Mdadm--zero-superblock/dev/sdd1 (Removal of RAID information)

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RAID (disk array) use