Linux Learning Note 10 (RAID Basics)

Disk Management is important for an OPS engineer. How to manage the data, you can not do without raid.

Content:

1. Common Types of RAID:

• RAID0 (Strip)

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• RAID1 (Mirror)

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• RAID5 (Parity check)

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• Raid1 + Raid0 (first 1 after 0)                         &NB Sp                          ,         &NB Sp       

• RAID0+RAID1 (first 0 after 1)

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• Raid5+raid0

• RAID0+RAID5 Ibid.

• Jbod is also commonly used, which can be expanded by increasing the number of hard drives.

  Summarize:

  Raid0	Performance improvement: Read, write Redundancy capability: None Space utilization: NS At least 2 pieces of disk
  Raid1	Performance gains: Read performance gains, write performance drops Redundancy capability: Available Space utilization: 1/2 At least 2 pieces of disk
  Raid5	Performance improvement: Read, write promotion Redundancy capability: Available Space utilization: (n-1)/n At least 3 plates required
  Raid1+raid0	Performance improvement: Read, write promotion Redundancy capability: Available Space utilization: 1/2 At least 4 plates required
  Raid0+raid1	Performance improvement: Read, write promotion Redundancy capability: Available Space utilization: 1/2 At least 4 plates required
  Raid5+raid0	Performance improvement: Read, write promotion Redundancy capability: Available Space utilization: (n-2)/n At least 6 plates required
  Jbod	Performance improvement: None Redundancy capability: None Space utilization: 100% Need at least 2 bucks.

2. Implement raid

RAID can be done through software simulations, where there is an environment for hardware RAID.

Logical raid:/dev/dm# #代表着编号

Some soft raid software uses:

Md:raid Module

• Mdadm (MD Manager): RAID any block device

Modal Commands:

Create a pattern

-C

Dedicated options:

-L: Level

-N #: Number of devices

-a {Yes|no}: whether to automatically create a device file for it

-c:chunk Size (chunk size), 2^n, default is 64K

-X #: Specify the number of free disks (after a disk is broken, it can be on top)

Management Mode

--add,--remove,--fail

mdadm/dev/md#--fail/dev/sda7

Monitoring mode

-F

Growth Model

-G

Assembly Mode

-A

View details of a RAID array

Mdadm-d/dev/md#

--detail

Stop array:

mdadm-s/dev/md#

--stop

Practice:

Create a RAID5 device with a space size of 10G and a chuck size of 32k, requiring the device to automatically mount to the/backup directory when it is powered on;

Create a 2G size RAID0 can be 4 x 512MB or 2 1G

Create a 2G size RAID1 can be 2 x 2G

Create a 2G size RAID5 can be 3 x 1G

• Watch: Executes the specified command periodically and displays the results in full-screen mode

-N #: Specifies the period length in seconds and defaults to 2

Format: Watch-n # ' COMMAND ' (double quotes also line)

Example: Watch "Cat/proc/mdstat"

• Save the current RAID information to a configuration file for later assembly:

mdamd-d--scan >/etc/mdadm.conf

Mdamd-a/dev/md# can be assembled directly.

Attention:

1. If a chunk is 64k a disk block is 4K (4096) then this means: a chunk is 16 disk blocks.

2. The MKE2FS has the-e stride function to adjust the chunk by a multiple of the block size, which optimizes the soft raid

3.rm-f/dev/md# should be mdadm-s/dev/md# (stop soft raid) before.

3 Specific processes: (Take Raid0 as an example)

1. Create/dev/sda{5,6,7}, and the type is RAID type

2.PARTPORBE/DEV/SDA (update partition information)

3.cat/proc/partitions (view partition)

4.mdadm-c/dev/md0-n 2-l 0-x 1-a yes/dev/sda{5,6,7}

5.mdadm-d/dev/md0 (can see the running situation)

This article from "Technology first" blog, declined reprint!

Linux Learning Note 10 (RAID Basics)