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RAID disk redundancy queue
2022-07-06 00:42:00 【Riding the waves】
RAID brief introduction
As servers are more and more widely used in enterprises , Data security , data storage , Data recovery , Storage speed and other aspects are becoming more and more important for enterprise users , and RAID Cards play a vital role in this process ,RAID The performance and characteristics of the card itself are often ignored by some users , In order to save costs, server manufacturers will also match some relatively elementary or even small brands RAID Card products , When there are problems in the use process, users just focus on the hard disk
RAID( Independent redundant disk array ) It's a kind of multi independent hard disk ( Physical hard disk ) Combine them in different ways to form a hard disk group ( Logical hard disk ), So as to provide higher storage performance and data backup capability than a single hard disk .
soft RAID And hard RAID
We want to implement on the server RAID, You can use disk array cards (RAID card ) To form a RAID, That is, hard RAID.RAID There is a special chip on the card for RAID Mission , So the performance is much better , And does not occupy the system performance , The disadvantage is that RAID Cards are expensive
If we don't want to spend money and want to use RAID, Then only use soft RAID 了 . soft RAID It refers to the realization through software RAID function , There is no extra cost , But it costs more server system performance , And the writing speed of data is faster than that of hard RAID slow
RAID It features N Block hard disk simultaneously accelerates reading speed and provides fault tolerance . Redundant disk array technology was born in 1987 year , Proposed by the University of California, Berkeley . According to different combinations of disk display , Can be RAID Divided into different levels . The level does not represent the level of Technology , Choose which one RAIDlevel Our products depend solely on the user's operating environment and Application , It has nothing to do with the level
RAID advantage :
1、 Improve I/O Ability , Disk parallel read and write
2、 Improve durability , Disk redundancy
3、 Level : Multiple disks work in different ways
4、raid How to achieve :
External disk array : Provide adaptability through expansion card
Built in raid: motherboard integrated raid controller , In the installation OS Before BIOS It's equipped with
Software raid: adopt OS To achieve , Hardware is used in production raid To achieve
raid The shortcomings of :
raid In the later stage of the array group, new members cannot be added to expand the overall capacity . for example : use 2 Block hard disk creation raid 0, Later cannot be in raid 0 Add a new hard disk . And that's where LVM Logical volume management function
RAID It can be divided into levels 0 To level 6, Often referred to as :RAID0、RAID1、RAID2、RAID3、RAID4、RAID5、RAID6
More classic RAID0、RAID1、RAID5、RAID6、RAID10 (RAID0+RAID1)
Grade | name | Number of hard disks | Total capacity | The number of bad sets allowed ( Maximum ) | function |
RAID0 | Banding | >=2 block | 2n+n | 0 block ( redundancy ) | High read-write performance , Capacity combination |
RAID1 | Mirror image | =2 block | n | 1 block ( redundancy ) | Synchronous backup , Data security |
RAID5 | Striping of distributed parity | >=3 block | 3n-n | 1 block ( redundancy ) | High read-write performance |
RAID6 | Striping of two groups of distributed parity | >=4 block | 4n-2n | 2 block ( redundancy ) | High read-write performance , Data security |
RAID10 | Mirror image + Banding | 4+2n block | Total capacity 50% | The bad half ( redundancy ) | Quantity combination + Synchronous backup |
mdadm command
linux Software in the system raid Management tool software :mdadm
Parameters | explain |
-D | Show RAID Device details |
-A | Add a previously defined RAID |
-B | Create one without super blocks RAID equipment |
-F | Option monitoring mode |
-G | change RAID Size or shape of equipment |
-I | Add device to RAID in , Or from RAID Delete device from |
-z | To form a RAID1、RAID4、RAID5、RAID6 After each RAID Space capacity acquired by members |
-s | Scan configuration files or /proc/mdstat Search for lost information |
-C | establish RAID equipment , hold RAID Information is written to each RAID Member super block |
-v | Show RAID Details of the creation process |
-B | establish RAID Another way , Not put RAID Information is written to each RAID In the super block of members |
-l | Appoint RAID The level of |
-n | Appoint RAID Number of active devices in |
-f | hold RAID Members are listed as having problems , To remove the member |
-r | hold RAID Members move out RAID equipment |
-a | towards RAID Add a member to the device |
--re-add | Put the recently removed RAID Members are added back to RAID In the device |
-E | see RAID Member details |
-c | Appoint chunk size , Create a RAID It defaults to 512kb |
-R | Start partial assembly RAID |
-S | Discontinue use RAID equipment , Release all resources |
-x | Specify initial RAID Number of spare members of the device |
--zero-superblock | If RAID The device contains a valid superblock , This block uses zero coverage |
Practice preparation
take linux Virtual machine shutdown , Add 5 block SCSI Interface 2GB The hard disk of , Create a snapshot “5 block 2G Hard disk ”, Then boot the virtual machine , perform lsblk The command displays a list of disk block devices
Raid practice : The request will linux Of system virtual machine 5 block 2G Hard disk for raid 5 Conduct management , Before the 4 The hard disk is organized into a file named md5 Of Raid5, among raid 5 The active disk of is the first 3 Block hard disk , The first 4 Hard disk as hot standby ( Spare tire 、 As a substitute ) disk .
lsblk # Display the list of disk devices
mdadm -Dsv # Show raid The equipment list
mdadm -C md5 -l 5 -n 3 -x 1 /dev/sd{b..e} # Create name as md5 Of raid 5 equipment
mdadm -D /dev/md/md5 # The display name is md5 Of raid 5 Device details
mdadm -Dsv # Show raid The equipment list
mdadm -Dsv > /etc/mdadm.conf # Generate raid The configuration file
——————————————————————————————————————
lsblk # Display the list of disk devices
mdadm -S /dev/md/md5 # Discontinue use md5 This raid equipment
mdadm -A /dev/md/md5 # Enable md5 This raid equipment
Be careful : To deactivate raid Enable the device later , Must ensure mdadm.conf The configuration file exists
practice : simulation md5 This Raid5 In the equipment sdc The hard disk is damaged , And then from md5 Remove from the array sdc This member , However, check md5 Device details . take sdc Remove the hard disk from the server , Install a new hard disk to Sdc On the slot of the hard disk . then sdf Hard disk added to md5 This raid 5 In the device group
mdadm -D /dev/md/md5 # The display name is md5 Of raid 5 Device details
mdadm /dev/md/md5 -f /dev/sdc # Appoint sdc The hard disk is bad (fail)
mdadm -D /dev/md/md5 # The display name is md5 Of raid 5 Device details
mdadm /dev/md/md5 -r /dev/sdc # take sdc Hard disk from md5 This raid Remove from group (remove)
mdadm /dev/md/md5 -a /dev/sdf # take sdf Hard disk add (add) To md5 This raid In the group
mdadm -D /dev/md/md5 # The display name is md5 Of raid 5 Device details
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