Nine. RAID (redundant Arrays of Independent Disk)

RAID action, RAID level, RAID implementation mode, MDADM

1. RAID action

Improved I/O capability: Parallel disk Read and write

Increased Durability: Disk redundancy

2. RAID level

Common level Raid0,raid1,raid5,raid10,raid50,jbod

RAID-0 Striped Volume strip, splitting data into chunk on different disks

1. Improve reading and writing ability

2. No fault-tolerant capability

3. Minimum number of disks 2

4. Free space: N*min (Disk1,disk2 ...)

　　　　

RAID-1 mirrored volume mirror, copying data into multiple copies on different disks

1. Reduce write ability, improve reading ability

2. Can break a hard drive at the same time

3. Minimum of two disks

4. Free disk space: 1*min (Disk1,disk2,disk3 ...)

　　　　

...

RAID-4 one disk to make a check disk, calculate the data of any piece of disk

1. Improve reading and writing ability

2. Can break a disk at the same time

3. At least three pieces of disk

4. Can space: (n-1) *min (Disk1,disk2 ...)

　　　　

RAID-5 each disk round-robin check disk, by calculating the data of any piece of disk can be obtained

1. Improve reading and writing ability

2. Can break a disk at the same time

3. At least 3 pieces of disk

4. Free space: (n-1) *min (Disk1,disk2,...)

　　　　

RAID-6 calculate two checksum values exist on different disks, each disk round-robin check disk

1. Improve reading and writing ability

2. Two disks can be damaged at the same time

3. At least 4 pieces of disk

4. Free space: (n-2) *min (Disk1,disk2 ...)

RAID-7

RAID-10 do RAID1 First, then do RAID0

1. Improve reading and writing ability

2. Up to half of the simultaneous bad disk

3. At least 4 pieces of disk

4. Free space: N*min (Disk1,disk2, ...) /2

　　　　

RAID-01 do RAID0 First, then do RAID1

JBOD Just a Bunch of Disk

Function: Combine multiple disk space into one continuous space use

Free space: sum (Disk1,disk2 ...)

3.RAID Implementation method

Hardware implementation

External disk array card to provide adaptive capability via expansion card

Internal raid, motherboard integrated RAID controller

Software implementation

4.mdadm-manage MD devices aka Linux software RAID

Mdadm [mode] <raiddevice> [options] <component-devices>

[Mode]

-C,--create

-N # Specifies how many disks to use for raid

-X # Specifies how many disks to use for hot spare disks

-L # Specify RAID level

-a {yes/no} automatically creates a target RAID device file

-C chunk_size Specify block size

-D View RAID details

-S Stop RAID device

<raiddevice> e.g/dev/md0

[Options]

-F Set the disk status to fail

-R Remove Disk device

-A Add disk device

<component-devices> E.G/DEV/SDB1/DEV/SDC1 ...

5. Cat/proc/mdstat View RAID Status

6. Create a soft raid step using Mdadm

1. Prepare the disk partition and change the ID to FD Linux RAID auto

2. Mdadm Create disk e.g Mdadm-c/dev/md0-n 3-x 1-l 5/dev/sd{b,c,d,e}1

3. Format the disk e.g Mkfs.etx4/dev/md0

　　

Nine. RAID (redundant Arrays of Independent Disk)